Merge pull request #190 from mamoe/command

重构 command 系统
2025-01-11 02:50:15 +08:00 · 2020-10-24 21:23:56 +08:00 · 2020-10-24 21:23:56 +08:00 · 15d0cdaf90
commit 15d0cdaf90
parent 4564531f8b f80c4b3fd1
59 changed files with 2093 additions and 941 deletions
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/BuiltInCommands.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/BuiltInCommands.kt
@ -15,7 +15,7 @@ import kotlinx.coroutines.sync.withLock
 import net.mamoe.mirai.alsoLogin
 import net.mamoe.mirai.console.MiraiConsole
 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.register
-import net.mamoe.mirai.console.command.description.*
+import net.mamoe.mirai.console.command.descriptor.*
 import net.mamoe.mirai.console.internal.command.CommandManagerImpl
 import net.mamoe.mirai.console.internal.command.CommandManagerImpl.allRegisteredCommands
 import net.mamoe.mirai.console.internal.util.runIgnoreException
@ -150,8 +150,8 @@ public object BuiltInCommands {
        ConsoleCommandOwner, "permission", "权限", "perm",
        description = "管理权限",
        overrideContext = buildCommandArgumentContext {
-            PermitteeId::class with PermitteeIdArgumentParser
-            Permission::class with PermissionIdArgumentParser.map { id ->
+            PermitteeId::class with PermitteeIdValueArgumentParser
+            Permission::class with PermissionIdValueArgumentParser.map { id ->
                kotlin.runCatching {
                    id.findCorrespondingPermissionOrFail()
                }.getOrElse { illegalArgument("指令不存在: $id", it) }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/Command.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/Command.kt
@ -11,25 +11,27 @@

 package net.mamoe.mirai.console.command

-import net.mamoe.kjbb.JvmBlockingBridge
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.register
+import net.mamoe.mirai.console.command.descriptor.CommandArgumentContextAware
+import net.mamoe.mirai.console.command.descriptor.CommandSignatureVariant
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
 import net.mamoe.mirai.console.command.java.JCommand
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
 import net.mamoe.mirai.console.permission.Permission
 import net.mamoe.mirai.console.permission.PermissionId
-import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi

 /**
 * 指令
 *
- * @see CommandManager.register 注册这个指令
+ * @see CommandManager.registerCommand 注册这个指令
 *
 * @see RawCommand 无参数解析, 接收原生参数的指令
 * @see CompositeCommand 复合指令
 * @see SimpleCommand 简单的, 支持参数自动解析的指令
 *
+ * @see CommandArgumentContextAware
+ *
 * @see JCommand 为 Java 用户添加协程帮助的 [Command]
 */
 public interface Command {
@ -48,18 +50,25 @@ public interface Command {
    @ResolveContext(COMMAND_NAME)
    public val secondaryNames: Array<out String>

+    /**
+     * 指令可能的参数列表.
+     */
+    @ConsoleExperimentalApi("Property name is experimental")
+    @ExperimentalCommandDescriptors
+    public val overloads: List<CommandSignatureVariant>
+
    /**
     * 用法说明, 用于发送给用户. [usage] 一般包含 [description].
     */
    public val usage: String

    /**
-     * 指令描述, 用于显示在 [BuiltInCommands.HelpCommand]
+     * 描述, 用于显示在 [BuiltInCommands.HelpCommand]
     */
    public val description: String

    /**
-     * 此指令所分配的权限.
+     * 为此指令分配的权限.
     *
     * ### 实现约束
     * - [Permission.id] 应由 [CommandOwner.permissionId] 创建. 因此保证相同的 [PermissionId.namespace]
@ -72,6 +81,8 @@ public interface Command {
     *
     * 会影响聊天语境中的解析.
     */
+    @ExperimentalCommandDescriptors
+    @ConsoleExperimentalApi
    public val prefixOptional: Boolean

    /**
@ -80,16 +91,6 @@ public interface Command {
     */
    public val owner: CommandOwner

-    /**
-     * 在指令被执行时调用.
-     *
-     * @param args 精确的指令参数. [MessageChain] 每个元素代表一个精确的参数.
-     *
-     * @see CommandManager.executeCommand 查看更多信息
-     */
-    @JvmBlockingBridge
-    public suspend fun CommandSender.onCommand(args: MessageChain)
-
    public companion object {

        /**
@ -109,19 +110,10 @@ public interface Command {
        public fun checkCommandName(@ResolveContext(COMMAND_NAME) name: String) {
            when {
                name.isBlank() -> throw IllegalArgumentException("Command name should not be blank.")
-                name.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces is not yet allowed in command name.")
+                name.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces are not yet allowed in command name.")
                name.contains(':') -> throw IllegalArgumentException("':' is forbidden in command name.")
                name.contains('.') -> throw IllegalArgumentException("'.' is forbidden in command name.")
            }
        }
    }
 }
-
-/**
- * 调用 [Command.onCommand]
- * @see Command.onCommand
- */
-@JvmSynthetic
-public suspend inline fun Command.onCommand(sender: CommandSender, args: MessageChain): Unit =
-    sender.onCommand(args)
-
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandExecuteResult.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandExecuteResult.kt
@ -12,6 +12,8 @@
 package net.mamoe.mirai.console.command

 import net.mamoe.mirai.console.command.CommandExecuteResult.CommandExecuteStatus
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.MessageChain
 import kotlin.contracts.contract
@ -21,6 +23,8 @@ import kotlin.contracts.contract
 *
 * @see CommandExecuteStatus
 */
+@ConsoleExperimentalApi("Not yet implemented")
+@ExperimentalCommandDescriptors
 public sealed class CommandExecuteResult {
    /** 指令最终执行状态 */
    public abstract val status: CommandExecuteStatus
@ -55,6 +59,21 @@ public sealed class CommandExecuteResult {
        public override val status: CommandExecuteStatus get() = CommandExecuteStatus.SUCCESSFUL
    }

+    /** 执行执行时发生了一个非法参数错误 */
+    public class IllegalArgument(
+        /** 指令执行时发生的错误 */
+        public override val exception: IllegalCommandArgumentException,
+        /** 尝试执行的指令 */
+        public override val command: Command,
+        /** 尝试执行的指令名 */
+        public override val commandName: String,
+        /** 基础分割后的实际参数列表, 元素类型可能为 [Message] 或 [String] */
+        public override val args: MessageChain
+    ) : CommandExecuteResult() {
+        /** 指令最终执行状态, 总是 [CommandExecuteStatus.EXECUTION_EXCEPTION] */
+        public override val status: CommandExecuteStatus get() = CommandExecuteStatus.ILLEGAL_ARGUMENT
+    }
+
    /** 指令执行过程出现了错误 */
    public class ExecutionFailed(
        /** 指令执行时发生的错误 */
@ -71,9 +90,9 @@ public sealed class CommandExecuteResult {
    }

    /** 没有匹配的指令 */
-    public class CommandNotFound(
+    public class UnresolvedCall(
        /** 尝试执行的指令名 */
-        public override val commandName: String
+        public override val commandName: String,
    ) : CommandExecuteResult() {
        /** 指令执行时发生的错误, 总是 `null` */
        public override val exception: Nothing? get() = null
@ -119,7 +138,9 @@ public sealed class CommandExecuteResult {
        COMMAND_NOT_FOUND,

        /** 权限不足 */
-        PERMISSION_DENIED
+        PERMISSION_DENIED,
+        /** 非法参数 */
+        ILLEGAL_ARGUMENT,
    }
 }

@ -138,6 +159,18 @@ public fun CommandExecuteResult.isSuccess(): Boolean {
    return this is CommandExecuteResult.Success
 }

+/**
+ * 当 [this] 为 [CommandExecuteResult.IllegalArgument] 时返回 `true`
+ */
+@JvmSynthetic
+public fun CommandExecuteResult.isIllegalArgument(): Boolean {
+    contract {
+        returns(true) implies (this@isIllegalArgument is CommandExecuteResult.IllegalArgument)
+        returns(false) implies (this@isIllegalArgument !is CommandExecuteResult.IllegalArgument)
+    }
+    return this is CommandExecuteResult.IllegalArgument
+}
+
 /**
 * 当 [this] 为 [CommandExecuteResult.ExecutionFailed] 时返回 `true`
 */
@ -151,7 +184,7 @@ public fun CommandExecuteResult.isExecutionException(): Boolean {
 }

 /**
- * 当 [this] 为 [CommandExecuteResult.ExecutionFailed] 时返回 `true`
+ * 当 [this] 为 [CommandExecuteResult.PermissionDenied] 时返回 `true`
 */
@JvmSynthetic
 public fun CommandExecuteResult.isPermissionDenied(): Boolean {
@ -163,19 +196,19 @@ public fun CommandExecuteResult.isPermissionDenied(): Boolean {
 }

 /**
- * 当 [this] 为 [CommandExecuteResult.ExecutionFailed] 时返回 `true`
+ * 当 [this] 为 [CommandExecuteResult.UnresolvedCall] 时返回 `true`
 */
@JvmSynthetic
 public fun CommandExecuteResult.isCommandNotFound(): Boolean {
    contract {
-        returns(true) implies (this@isCommandNotFound is CommandExecuteResult.CommandNotFound)
-        returns(false) implies (this@isCommandNotFound !is CommandExecuteResult.CommandNotFound)
+        returns(true) implies (this@isCommandNotFound is CommandExecuteResult.UnresolvedCall)
+        returns(false) implies (this@isCommandNotFound !is CommandExecuteResult.UnresolvedCall)
    }
-    return this is CommandExecuteResult.CommandNotFound
+    return this is CommandExecuteResult.UnresolvedCall
 }

 /**
- * 当 [this] 为 [CommandExecuteResult.ExecutionFailed] 或 [CommandExecuteResult.CommandNotFound] 时返回 `true`
+ * 当 [this] 为 [CommandExecuteResult.ExecutionFailed], [CommandExecuteResult.IllegalArgument] 或 [CommandExecuteResult.UnresolvedCall] 时返回 `true`
 */
@JvmSynthetic
 public fun CommandExecuteResult.isFailure(): Boolean {
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandManager.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandManager.kt
@ -8,7 +8,7 @@
 */

@file:Suppress(
-    "NOTHING_TO_INLINE", "unused", "INVISIBLE_MEMBER", "INVISIBLE_REFERENCE", "RESULT_CLASS_IN_RETURN_TYPE",
+    "NOTHING_TO_INLINE", "unused",
    "MemberVisibilityCanBePrivate", "INAPPLICABLE_JVM_NAME"
 )
@file:JvmName("CommandManagerKt")
@ -16,21 +16,21 @@
 package net.mamoe.mirai.console.command

 import net.mamoe.kjbb.JvmBlockingBridge
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.command.parse.CommandCallParser
+import net.mamoe.mirai.console.command.resolve.CommandCallResolver
 import net.mamoe.mirai.console.internal.command.CommandManagerImpl
 import net.mamoe.mirai.console.internal.command.CommandManagerImpl.executeCommand
+import net.mamoe.mirai.console.internal.command.executeCommandImpl
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
 import net.mamoe.mirai.message.data.*

 /**
 * 指令管理器
 */
 public interface CommandManager {
-    /**
-     * 获取已经注册了的属于这个 [CommandOwner] 的指令列表.
-     *
-     * @return 这一时刻的浅拷贝.
-     */
-    public val CommandOwner.registeredCommands: List<Command>
-
    /**
     * 获取所有已经注册了指令列表.
     *
@ -44,9 +44,17 @@ public interface CommandManager {
    public val commandPrefix: String

    /**
-     * 取消注册所有属于 [this] 的指令
+     * 获取已经注册了的属于这个 [CommandOwner] 的指令列表.
+     *
+     * @return 这一时刻的浅拷贝.
     */
-    public fun CommandOwner.unregisterAllCommands()
+    public fun getRegisteredCommands(owner: CommandOwner): List<Command>
+
+
+    /**
+     * 取消注册所有属于 [owner] 的指令
+     */
+    public fun unregisterAllCommands(owner: CommandOwner)

    /**
     * 注册一个指令.
@ -65,35 +73,31 @@ public interface CommandManager {
     *
     * 注意: [内建指令][BuiltInCommands] 也可以被覆盖.
     */
-    @JvmName("registerCommand")
-    public fun Command.register(override: Boolean = false): Boolean
+    public fun registerCommand(command: Command, override: Boolean = false): Boolean

    /**
     * 查找并返回重名的指令. 返回重名指令.
     */
-    @JvmName("findCommandDuplicate")
-    public fun Command.findDuplicate(): Command?
+    public fun findDuplicateCommand(command: Command): Command?

    /**
     * 取消注册这个指令.
     *
     * 若指令未注册, 返回 `false`.
     */
-    @JvmName("unregisterCommand")
-    public fun Command.unregister(): Boolean
+    public fun unregisterCommand(command: Command): Boolean

    /**
-     * 当 [this] 已经 [注册][register] 时返回 `true`
+     * 当 [command] 已经 [注册][registerCommand] 时返回 `true`
     */
-    @JvmName("isCommandRegistered")
-    public fun Command.isRegistered(): Boolean
+    public fun isCommandRegistered(command: Command): Boolean

    /**
     * 解析并执行一个指令.
     *
-     * 如要避免参数解析, 请使用 [Command.onCommand]
-     *
     * ### 指令解析流程
+     * 1. [CommandCallParser] 将 [MessageChain] 解析为 [CommandCall]
+     * 2. [CommandCallResolver] 将 [CommandCall] 解析为 []
     * 1. [message] 的第一个消息元素的 [内容][Message.contentToString] 被作为指令名, 在已注册指令列表中搜索. (包含 [Command.prefixOptional] 相关的处理)
     * 2. 参数语法分析.
     *   在当前的实现下, [message] 被以空格和 [SingleMessage] 分割.
@ -101,19 +105,113 @@ public interface CommandManager {
     *   注意: 字符串与消息元素之间不需要空格, 会被强制分割. 如 "bar[mirai:image:]" 会被分割为 "bar" 和 [Image] 类型的消息元素.
     * 3. 参数解析. 各类型指令实现不同. 详见 [RawCommand], [CompositeCommand], [SimpleCommand]
     *
-     * ### 未来的扩展
-     * 在将来, 参数语法分析过程可能会被扩展, 允许插件自定义处理方式, 因此可能不会简单地使用空格分隔.
+     * ### 扩展
+     * 参数语法分析过程可能会被扩展, 插件可以自定义处理方式 ([CommandCallParser]), 因此可能不会简单地使用空格分隔.
     *
     * @param message 一条完整的指令. 如 "/managers add 123456.123456"
     * @param checkPermission 为 `true` 时检查权限
     *
+     * @see CommandCallParser
+     * @see CommandCallResolver
+     *
+     * @see CommandSender.executeCommand
+     * @see Command.execute
+     *
     * @return 执行结果
     */
+    @ExperimentalCommandDescriptors
    @JvmBlockingBridge
-    public suspend fun CommandSender.executeCommand(
+    public suspend fun executeCommand(
+        caller: CommandSender,
        message: Message,
        checkPermission: Boolean = true,
-    ): CommandExecuteResult
+    ): CommandExecuteResult {
+        return executeCommandImpl(message, caller, checkPermission)
+    }
+
+    /**
+     * 执行一个确切的指令
+     *
+     * @param command 目标指令
+     * @param arguments 参数列表
+     *
+     * @see executeCommand 获取更多信息
+     * @see Command.execute
+     */
+    @ConsoleExperimentalApi
+    @JvmName("executeCommand")
+    @ExperimentalCommandDescriptors
+    @JvmSynthetic
+    public suspend fun executeCommand(
+        sender: CommandSender,
+        command: Command,
+        arguments: Message = EmptyMessageChain,
+        checkPermission: Boolean = true,
+    ): CommandExecuteResult {
+        // TODO: 2020/10/18  net.mamoe.mirai.console.command.CommandManager.execute
+        val chain = buildMessageChain {
+            append(CommandManager.commandPrefix)
+            append(command.primaryName)
+            append(' ')
+            append(arguments)
+        }
+        return CommandManager.executeCommand(sender, chain, checkPermission)
+    }
+
+    /**
+     * 从 [指令名称][commandName] 匹配对应的 [Command].
+     *
+     * #### 实现细节
+     * - [commandName] 带有 [commandPrefix] 时可以匹配到所有指令
+     * - [commandName] 不带有 [commandPrefix] 时只能匹配到 [Command.prefixOptional] 的指令
+     *
+     * @param commandName 可能带有或不带有 [commandPrefix].
+     */
+    public fun matchCommand(commandName: String): Command?
+
+    public companion object INSTANCE : CommandManager by CommandManagerImpl {
+
+        /**
+         * @see CommandManager.getRegisteredCommands
+         */
+        @get:JvmName("registeredCommands0")
+        @get:JvmSynthetic
+        public inline val CommandOwner.registeredCommands: List<Command>
+            get() = getRegisteredCommands(this)
+
+        /**
+         * @see CommandManager.registerCommand
+         */
+        @JvmSynthetic
+        public inline fun Command.register(override: Boolean = false): Boolean = registerCommand(this, override)
+
+        /**
+         * @see CommandManager.unregisterCommand
+         */
+        @JvmSynthetic
+        public inline fun Command.unregister(): Boolean = unregisterCommand(this)
+
+        /**
+         * @see CommandManager.isCommandRegistered
+         */
+        @get:JvmSynthetic
+        public inline val Command.isRegistered: Boolean
+            get() = isCommandRegistered(this)
+
+        /**
+         * @see CommandManager.unregisterAll
+         */
+        @JvmSynthetic
+        public inline fun CommandOwner.unregisterAll(): Unit = unregisterAllCommands(this)
+
+        /**
+         * @see CommandManager.findDuplicate
+         */
+        @JvmSynthetic
+        public inline fun Command.findDuplicate(): Command? = findDuplicateCommand(this)
+
+    }
+}

 /**
 * 解析并执行一个指令
@ -124,95 +222,37 @@ public interface CommandManager {
 * @return 执行结果
 * @see executeCommand
 */
-    @JvmBlockingBridge
-    public suspend fun CommandSender.executeCommand(
+@JvmName("execute0")
+@ExperimentalCommandDescriptors
+@JvmSynthetic
+public suspend inline fun CommandSender.executeCommand(
    message: String,
    checkPermission: Boolean = true,
-    ): CommandExecuteResult = executeCommand(PlainText(message).asMessageChain(), checkPermission)
+): CommandExecuteResult = CommandManager.executeCommand(this, PlainText(message).asMessageChain(), checkPermission)
+

 /**
 * 执行一个确切的指令
 * @see executeCommand 获取更多信息
 */
-    @JvmBlockingBridge
-    @JvmName("executeCommand")
-    public suspend fun Command.execute(
+@JvmName("execute0")
+@ExperimentalCommandDescriptors
+@JvmSynthetic
+public suspend inline fun Command.execute(
    sender: CommandSender,
    arguments: Message = EmptyMessageChain,
    checkPermission: Boolean = true,
-    ): CommandExecuteResult
+): CommandExecuteResult = CommandManager.executeCommand(sender, this, arguments, checkPermission)

 /**
 * 执行一个确切的指令
 * @see executeCommand 获取更多信息
 */
-    @JvmBlockingBridge
-    @JvmName("executeCommand")
-    public suspend fun Command.execute(
+@JvmName("execute0")
+@ExperimentalCommandDescriptors
+@JvmSynthetic
+public suspend inline fun Command.execute(
    sender: CommandSender,
    arguments: String = "",
    checkPermission: Boolean = true,
-    ): CommandExecuteResult = execute(sender, PlainText(arguments).asMessageChain(), checkPermission)
-
-    public companion object INSTANCE : CommandManager by CommandManagerImpl {
-        // TODO: 2020/8/20 https://youtrack.jetbrains.com/issue/KT-41191
-
-        override val CommandOwner.registeredCommands: List<Command> get() = CommandManagerImpl.run { this@registeredCommands.registeredCommands }
-        override fun CommandOwner.unregisterAllCommands(): Unit = CommandManagerImpl.run { unregisterAllCommands() }
-        override fun Command.register(override: Boolean): Boolean = CommandManagerImpl.run { register(override) }
-        override fun Command.findDuplicate(): Command? = CommandManagerImpl.run { findDuplicate() }
-        override fun Command.unregister(): Boolean = CommandManagerImpl.run { unregister() }
-        override fun Command.isRegistered(): Boolean = CommandManagerImpl.run { isRegistered() }
-        override val commandPrefix: String get() = CommandManagerImpl.commandPrefix
-        override val allRegisteredCommands: List<Command>
-            get() = CommandManagerImpl.allRegisteredCommands
-
-
-        override suspend fun Command.execute(
-            sender: CommandSender,
-            arguments: Message,
-            checkPermission: Boolean,
-        ): CommandExecuteResult =
-            CommandManagerImpl.run { execute(sender, arguments = arguments, checkPermission = checkPermission) }
-
-        override suspend fun CommandSender.executeCommand(
-            message: String,
-            checkPermission: Boolean,
-        ): CommandExecuteResult = CommandManagerImpl.run { executeCommand(message, checkPermission) }
-
-        override suspend fun Command.execute(
-            sender: CommandSender,
-            arguments: String,
-            checkPermission: Boolean,
-        ): CommandExecuteResult = CommandManagerImpl.run { execute(sender, arguments, checkPermission) }
-
-        override suspend fun CommandSender.executeCommand(
-            message: Message,
-            checkPermission: Boolean,
-        ): CommandExecuteResult = CommandManagerImpl.run { executeCommand(message, checkPermission) }
-
-        /**
-         * 执行一个确切的指令
-         * @see execute 获取更多信息
-         */
-        public suspend fun CommandSender.execute(
-            command: Command,
-            arguments: Message,
-            checkPermission: Boolean = true,
-        ): CommandExecuteResult {
-            return command.execute(this, arguments, checkPermission)
-        }
-
-        /**
-         * 执行一个确切的指令
-         * @see execute 获取更多信息
-         */
-        public suspend fun CommandSender.execute(
-            command: Command,
-            arguments: String,
-            checkPermission: Boolean = true,
-        ): CommandExecuteResult {
-            return command.execute(this, arguments, checkPermission)
-        }
-    }
-}
+): CommandExecuteResult = execute(sender, PlainText(arguments), checkPermission)
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandSender.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandSender.kt
@ -20,15 +20,14 @@ import kotlinx.coroutines.launch
 import net.mamoe.kjbb.JvmBlockingBridge
 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.console.MiraiConsole
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.execute
 import net.mamoe.mirai.console.command.CommandSender.Companion.asCommandSender
 import net.mamoe.mirai.console.command.CommandSender.Companion.asMemberCommandSender
 import net.mamoe.mirai.console.command.CommandSender.Companion.asTempCommandSender
 import net.mamoe.mirai.console.command.CommandSender.Companion.toCommandSender
-import net.mamoe.mirai.console.command.description.CommandArgumentParserException
+import net.mamoe.mirai.console.command.descriptor.CommandArgumentParserException
 import net.mamoe.mirai.console.internal.MiraiConsoleImplementationBridge
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
 import net.mamoe.mirai.console.internal.data.castOrNull
+import net.mamoe.mirai.console.internal.data.qualifiedNameOrTip
 import net.mamoe.mirai.console.internal.plugin.rootCauseOrSelf
 import net.mamoe.mirai.console.permission.AbstractPermitteeId
 import net.mamoe.mirai.console.permission.Permittee
@ -281,6 +280,13 @@ public sealed class AbstractCommandSender : CommandSender, CoroutineScope {
        if (this is CommandSenderOnMessage<*>) {
            val cause = e.rootCauseOrSelf

+            // TODO: 2020/10/17
+            //      CommandArgumentParserException 作为 IllegalCommandArgumentException 不会再进入此函数
+            //      已在
+            //       - [console]  CommandManagerImpl.commandListener
+            //       - [terminal] ConsoleThread.kt
+            //      处理
+
            val message = cause
                .takeIf { it is CommandArgumentParserException }?.message
                ?: "${cause::class.simpleName.orEmpty()}: ${cause.message}"
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CompositeCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CompositeCommand.kt
@ -17,14 +17,13 @@

 package net.mamoe.mirai.console.command

-import net.mamoe.mirai.console.command.description.*
+import net.mamoe.mirai.console.command.descriptor.*
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
-import net.mamoe.mirai.console.internal.command.AbstractReflectionCommand
+import net.mamoe.mirai.console.internal.command.CommandReflector
 import net.mamoe.mirai.console.internal.command.CompositeCommandSubCommandAnnotationResolver
 import net.mamoe.mirai.console.permission.Permission
 import net.mamoe.mirai.console.util.ConsoleExperimentalApi
-import net.mamoe.mirai.message.data.MessageChain
 import kotlin.annotation.AnnotationRetention.RUNTIME
 import kotlin.annotation.AnnotationTarget.FUNCTION

@ -90,16 +89,26 @@ public abstract class CompositeCommand(
    parentPermission: Permission = owner.parentPermission,
    prefixOptional: Boolean = false,
    overrideContext: CommandArgumentContext = EmptyCommandArgumentContext,
-) : Command, AbstractReflectionCommand(owner, primaryName, secondaryNames = secondaryNames, description, parentPermission, prefixOptional),
+) : Command, AbstractCommand(owner, primaryName, secondaryNames = secondaryNames, description, parentPermission, prefixOptional),
    CommandArgumentContextAware {

+    private val reflector by lazy { CommandReflector(this, CompositeCommandSubCommandAnnotationResolver) }
+
+    @ExperimentalCommandDescriptors
+    public final override val overloads: List<CommandSignatureVariantFromKFunction> by lazy {
+        reflector.findSubCommands()
+    }
+
    /**
     * 自动根据带有 [SubCommand] 注解的函数签名生成 [usage]. 也可以被覆盖.
     */
-    public override val usage: String get() = super.usage
+    public override val usage: String by lazy {
+        @OptIn(ExperimentalCommandDescriptors::class)
+        reflector.generateUsage(overloads)
+    }

    /**
-     * [CommandArgumentParser] 的环境
+     * [CommandValueArgumentParser] 的环境
     */
    public final override val context: CommandArgumentContext = CommandArgumentContext.Builtins + overrideContext

@ -123,20 +132,6 @@ public abstract class CompositeCommand(
    @Retention(RUNTIME)
    @Target(AnnotationTarget.VALUE_PARAMETER)
    protected annotation class Name(val value: String)
-
-    public final override suspend fun CommandSender.onCommand(args: MessageChain) {
-        matchSubCommand(args)?.parseAndExecute(this, args, true) ?: kotlin.run {
-            defaultSubCommand.onCommand(this, args)
-        }
-    }
-
-
-    protected override suspend fun CommandSender.onDefault(rawArgs: MessageChain) {
-        sendMessage(usage)
-    }
-
-    internal final override val subCommandAnnotationResolver: SubCommandAnnotationResolver
-        get() = CompositeCommandSubCommandAnnotationResolver
 }


--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/IllegalCommandArgumentException.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/IllegalCommandArgumentException.kt
@ -0,0 +1,29 @@
+/*
+ * Copyright 2019-2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AFFERO GENERAL PUBLIC LICENSE version 3 license that can be found via the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ *
+ */
+
+@file:Suppress("unused")
+
+package net.mamoe.mirai.console.command
+
+import net.mamoe.mirai.console.command.descriptor.CommandArgumentParserException
+
+/**
+ * 在处理参数时遇到的 _正常_ 错误. 如参数不符合规范, 参数值越界等.
+ *
+ * [message] 将会发送给指令调用方.
+ *
+ * @see CommandArgumentParserException
+ */
+public open class IllegalCommandArgumentException : IllegalArgumentException {
+    public constructor() : super()
+    public constructor(message: String?) : super(message)
+    public constructor(message: String?, cause: Throwable?) : super(message, cause)
+    public constructor(cause: Throwable?) : super(cause)
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/RawCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/RawCommand.kt
@ -11,14 +11,17 @@

 package net.mamoe.mirai.console.command

-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.execute
 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
+import net.mamoe.mirai.console.command.descriptor.*
 import net.mamoe.mirai.console.command.java.JRawCommand
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
 import net.mamoe.mirai.console.internal.command.createOrFindCommandPermission
+import net.mamoe.mirai.console.internal.data.typeOf0
 import net.mamoe.mirai.console.permission.Permission
+import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.message.data.buildMessageChain

 /**
 * 无参数解析, 接收原生参数的指令.
@ -52,6 +55,18 @@ public abstract class RawCommand(
 ) : Command {
    public override val permission: Permission by lazy { createOrFindCommandPermission(parentPermission) }

+    @ExperimentalCommandDescriptors
+    override val overloads: List<CommandSignatureVariant> = listOf(
+        CommandSignatureVariantImpl(
+            receiverParameter = CommandReceiverParameter(false, typeOf0<CommandSender>()),
+            valueParameters = listOf(AbstractCommandValueParameter.UserDefinedType.createRequired<Array<out Message>>("args", true))
+        ) { call ->
+            val sender = call.caller
+            val arguments = call.rawValueArguments
+            sender.onCommand(buildMessageChain { arguments.forEach { +it.value } })
+        }
+    )
+
    /**
     * 在指令被执行时调用.
     *
@ -59,7 +74,7 @@ public abstract class RawCommand(
     *
     * @see CommandManager.execute 查看更多信息
     */
-    public abstract override suspend fun CommandSender.onCommand(args: MessageChain)
+    public abstract suspend fun CommandSender.onCommand(args: MessageChain)
 }


--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/SimpleCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/SimpleCommand.kt
@ -18,20 +18,23 @@
 package net.mamoe.mirai.console.command

 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
-import net.mamoe.mirai.console.command.description.*
+import net.mamoe.mirai.console.command.descriptor.*
 import net.mamoe.mirai.console.command.java.JSimpleCommand
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
-import net.mamoe.mirai.console.internal.command.AbstractReflectionCommand
+import net.mamoe.mirai.console.internal.command.CommandReflector
+import net.mamoe.mirai.console.internal.command.IllegalCommandDeclarationException
 import net.mamoe.mirai.console.internal.command.SimpleCommandSubCommandAnnotationResolver
 import net.mamoe.mirai.console.permission.Permission
-import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import kotlin.annotation.AnnotationTarget.FUNCTION
+import kotlin.annotation.AnnotationTarget.VALUE_PARAMETER

 /**
 * 简单的, 支持参数自动解析的指令.
 *
 * 要查看指令解析流程, 参考 [CommandManager.executeCommand]
- * 要查看参数解析方式, 参考 [CommandArgumentParser]
+ * 要查看参数解析方式, 参考 [CommandValueArgumentParser]
 *
 * Kotlin 实现:
 * ```
@ -58,39 +61,41 @@ public abstract class SimpleCommand(
    parentPermission: Permission = owner.parentPermission,
    prefixOptional: Boolean = false,
    overrideContext: CommandArgumentContext = EmptyCommandArgumentContext,
-) : Command, AbstractReflectionCommand(owner, primaryName, secondaryNames = secondaryNames, description, parentPermission, prefixOptional),
+) : Command, AbstractCommand(owner, primaryName, secondaryNames = secondaryNames, description, parentPermission, prefixOptional),
    CommandArgumentContextAware {

+    private val reflector by lazy { CommandReflector(this, SimpleCommandSubCommandAnnotationResolver) }
+
+    @ExperimentalCommandDescriptors
+    public final override val overloads: List<CommandSignatureVariantFromKFunction> by lazy {
+        reflector.findSubCommands().also {
+            if (it.isEmpty())
+                throw IllegalCommandDeclarationException(this, "SimpleCommand must have at least one subcommand, whereas zero present.")
+        }
+    }
+
    /**
     * 自动根据带有 [Handler] 注解的函数签名生成 [usage]. 也可以被覆盖.
     */
-    public override val usage: String get() = super.usage
+    public override val usage: String by lazy {
+        @OptIn(ExperimentalCommandDescriptors::class)
+        reflector.generateUsage(overloads)
+    }

    /**
     * 标注指令处理器
     */
+    @Target(FUNCTION)
    protected annotation class Handler

+    /** 参数名, 将参与构成 [usage] */
+    @ConsoleExperimentalApi("Classname might change")
+    @Target(VALUE_PARAMETER)
+    protected annotation class Name(val value: String)
+
    /**
     * 指令参数环境. 默认为 [CommandArgumentContext.Builtins] `+` `overrideContext`
     */
    public override val context: CommandArgumentContext = CommandArgumentContext.Builtins + overrideContext
-
-    public final override suspend fun CommandSender.onCommand(args: MessageChain) {
-        subCommands.single().parseAndExecute(this, args, false)
-    }
-
-    internal override fun checkSubCommand(subCommands: Array<SubCommandDescriptor>) {
-        super.checkSubCommand(subCommands)
-        check(subCommands.size == 1) { "There can only be exactly one function annotated with Handler at this moment as overloading is not yet supported." }
-    }
-
-    @Deprecated("prohibited", level = DeprecationLevel.HIDDEN)
-    internal override suspend fun CommandSender.onDefault(rawArgs: MessageChain) {
-        sendMessage(usage)
-    }
-
-    internal final override val subCommandAnnotationResolver: SubCommandAnnotationResolver
-        get() = SimpleCommandSubCommandAnnotationResolver
 }

--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentContext.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentContext.kt
@ -9,18 +9,19 @@

@file:Suppress("NOTHING_TO_INLINE", "INVISIBLE_MEMBER", "INVISIBLE_REFERENCE", "unused", "MemberVisibilityCanBePrivate")

-package net.mamoe.mirai.console.command.description
+package net.mamoe.mirai.console.command.descriptor

 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.console.command.CommandSender
 import net.mamoe.mirai.console.command.CompositeCommand
 import net.mamoe.mirai.console.command.SimpleCommand
-import net.mamoe.mirai.console.command.description.CommandArgumentContext.ParserPair
+import net.mamoe.mirai.console.command.descriptor.CommandArgumentContext.ParserPair
 import net.mamoe.mirai.console.permission.PermissionId
 import net.mamoe.mirai.console.permission.PermitteeId
 import net.mamoe.mirai.console.util.ConsoleExperimentalApi
 import net.mamoe.mirai.contact.*
 import net.mamoe.mirai.message.data.Image
+import net.mamoe.mirai.message.data.MessageContent
 import net.mamoe.mirai.message.data.PlainText
 import kotlin.internal.LowPriorityInOverloadResolution
 import kotlin.reflect.KClass
@ -28,7 +29,7 @@ import kotlin.reflect.full.isSubclassOf


 /**
- * 指令参数环境, 即 [CommandArgumentParser] 的集合, 用于 [CompositeCommand] 和 [SimpleCommand].
+ * 指令参数环境, 即 [CommandValueArgumentParser] 的集合, 用于 [CompositeCommand] 和 [SimpleCommand].
 *
 * 在指令解析时, 总是从 [CommandArgumentContextAware.context] 搜索相关解析器
 *
@ -37,20 +38,20 @@ import kotlin.reflect.full.isSubclassOf
 * @see SimpleCommandArgumentContext 简单实现
 * @see EmptyCommandArgumentContext 空实现, 类似 [emptyList]
 *
- * @see CommandArgumentContext.Builtins 内建 [CommandArgumentParser]
+ * @see CommandArgumentContext.Builtins 内建 [CommandValueArgumentParser]
 *
 * @see buildCommandArgumentContext DSL 构造
 */
 public interface CommandArgumentContext {
    /**
-     * [KClass] 到 [CommandArgumentParser] 的匹配
+     * [KClass] 到 [CommandValueArgumentParser] 的匹配
     */
    public data class ParserPair<T : Any>(
        val klass: KClass<T>,
-        val parser: CommandArgumentParser<T>,
+        val parser: CommandValueArgumentParser<T>,
    )

-    public operator fun <T : Any> get(klass: KClass<out T>): CommandArgumentParser<T>?
+    public operator fun <T : Any> get(klass: KClass<out T>): CommandValueArgumentParser<T>?

    public fun toList(): List<ParserPair<*>>

@ -65,30 +66,32 @@ public interface CommandArgumentContext {
    }

    /**
-     * 内建的默认 [CommandArgumentParser]
+     * 内建的默认 [CommandValueArgumentParser]
     */
    public object Builtins : CommandArgumentContext by (buildCommandArgumentContext {
-        Int::class with IntArgumentParser
-        Byte::class with ByteArgumentParser
-        Short::class with ShortArgumentParser
-        Boolean::class with BooleanArgumentParser
-        String::class with StringArgumentParser
-        Long::class with LongArgumentParser
-        Double::class with DoubleArgumentParser
-        Float::class with FloatArgumentParser
+        Int::class with IntValueArgumentParser
+        Byte::class with ByteValueArgumentParser
+        Short::class with ShortValueArgumentParser
+        Boolean::class with BooleanValueArgumentParser
+        String::class with StringValueArgumentParser
+        Long::class with LongValueArgumentParser
+        Double::class with DoubleValueArgumentParser
+        Float::class with FloatValueArgumentParser

-        Image::class with ImageArgumentParser
-        PlainText::class with PlainTextArgumentParser
+        Image::class with ImageValueArgumentParser
+        PlainText::class with PlainTextValueArgumentParser

-        Contact::class with ExistingContactArgumentParser
-        User::class with ExistingUserArgumentParser
-        Member::class with ExistingMemberArgumentParser
-        Group::class with ExistingGroupArgumentParser
-        Friend::class with ExistingFriendArgumentParser
-        Bot::class with ExistingBotArgumentParser
+        Contact::class with ExistingContactValueArgumentParser
+        User::class with ExistingUserValueArgumentParser
+        Member::class with ExistingMemberValueArgumentParser
+        Group::class with ExistingGroupValueArgumentParser
+        Friend::class with ExistingFriendValueArgumentParser
+        Bot::class with ExistingBotValueArgumentParser

-        PermissionId::class with PermissionIdArgumentParser
-        PermitteeId::class with PermitteeIdArgumentParser
+        PermissionId::class with PermissionIdValueArgumentParser
+        PermitteeId::class with PermitteeIdValueArgumentParser
+
+        MessageContent::class with RawContentValueArgumentParser
    })
 }

@ -100,7 +103,7 @@ public interface CommandArgumentContext {
 */
 public interface CommandArgumentContextAware {
    /**
-     * [CommandArgumentParser] 的集合
+     * [CommandValueArgumentParser] 的集合
     */
    public val context: CommandArgumentContext
 }
@ -114,7 +117,7 @@ public operator fun CommandArgumentContext.plus(replacer: CommandArgumentContext
    if (replacer == EmptyCommandArgumentContext) return this
    if (this == EmptyCommandArgumentContext) return replacer
    return object : CommandArgumentContext {
-        override fun <T : Any> get(klass: KClass<out T>): CommandArgumentParser<T>? =
+        override fun <T : Any> get(klass: KClass<out T>): CommandValueArgumentParser<T>? =
            replacer[klass] ?: this@plus[klass]

        override fun toList(): List<ParserPair<*>> = replacer.toList() + this@plus.toList()
@ -129,8 +132,8 @@ public operator fun CommandArgumentContext.plus(replacer: List<ParserPair<*>>):
    if (this == EmptyCommandArgumentContext) return SimpleCommandArgumentContext(replacer)
    return object : CommandArgumentContext {
        @Suppress("UNCHECKED_CAST")
-        override fun <T : Any> get(klass: KClass<out T>): CommandArgumentParser<T>? =
-            replacer.firstOrNull { klass.isSubclassOf(it.klass) }?.parser as CommandArgumentParser<T>?
+        override fun <T : Any> get(klass: KClass<out T>): CommandValueArgumentParser<T>? =
+            replacer.firstOrNull { klass.isSubclassOf(it.klass) }?.parser as CommandValueArgumentParser<T>?
                ?: this@plus[klass]

        override fun toList(): List<ParserPair<*>> = replacer.toList() + this@plus.toList()
@ -146,9 +149,9 @@ public operator fun CommandArgumentContext.plus(replacer: List<ParserPair<*>>):
 public class SimpleCommandArgumentContext(
    public val list: List<ParserPair<*>>,
 ) : CommandArgumentContext {
-    override fun <T : Any> get(klass: KClass<out T>): CommandArgumentParser<T>? =
+    override fun <T : Any> get(klass: KClass<out T>): CommandValueArgumentParser<T>? =
        (this.list.firstOrNull { klass == it.klass }?.parser
-            ?: this.list.firstOrNull { klass.isSubclassOf(it.klass) }?.parser) as CommandArgumentParser<T>?
+            ?: this.list.firstOrNull { klass.isSubclassOf(it.klass) }?.parser) as CommandValueArgumentParser<T>?

    override fun toList(): List<ParserPair<*>> = list
 }
@ -160,7 +163,7 @@ public class SimpleCommandArgumentContext(
 * ```
 * val context = buildCommandArgumentContext {
 *     Int::class with IntArgParser
- *     Member::class with ExistMemberArgParser
+ *     Member::class with ExistingMemberArgParser
 *     Group::class with { s: String, sender: CommandSender ->
 *          Bot.getInstance(s.toLong()).getGroup(s.toLong())
 *     }
@ -200,14 +203,14 @@ public class CommandArgumentContextBuilder : MutableList<ParserPair<*>> by mutab
     * 添加一个指令解析器.
     */
    @JvmName("add")
-    public infix fun <T : Any> Class<T>.with(parser: CommandArgumentParser<T>): CommandArgumentContextBuilder =
+    public infix fun <T : Any> Class<T>.with(parser: CommandValueArgumentParser<T>): CommandArgumentContextBuilder =
        this.kotlin with parser

    /**
     * 添加一个指令解析器
     */
    @JvmName("add")
-    public inline infix fun <T : Any> KClass<T>.with(parser: CommandArgumentParser<T>): CommandArgumentContextBuilder {
+    public inline infix fun <T : Any> KClass<T>.with(parser: CommandValueArgumentParser<T>): CommandArgumentContextBuilder {
        add(ParserPair(this, parser))
        return this@CommandArgumentContextBuilder
    }
@ -218,9 +221,9 @@ public class CommandArgumentContextBuilder : MutableList<ParserPair<*>> by mutab
    @JvmSynthetic
    @LowPriorityInOverloadResolution
    public inline infix fun <T : Any> KClass<T>.with(
-        crossinline parser: CommandArgumentParser<T>.(s: String, sender: CommandSender) -> T,
+        crossinline parser: CommandValueArgumentParser<T>.(s: String, sender: CommandSender) -> T,
    ): CommandArgumentContextBuilder {
-        add(ParserPair(this, object : CommandArgumentParser<T> {
+        add(ParserPair(this, object : CommandValueArgumentParser<T> {
            override fun parse(raw: String, sender: CommandSender): T = parser(raw, sender)
        }))
        return this@CommandArgumentContextBuilder
@ -231,16 +234,16 @@ public class CommandArgumentContextBuilder : MutableList<ParserPair<*>> by mutab
     */
    @JvmSynthetic
    public inline infix fun <T : Any> KClass<T>.with(
-        crossinline parser: CommandArgumentParser<T>.(s: String) -> T,
+        crossinline parser: CommandValueArgumentParser<T>.(s: String) -> T,
    ): CommandArgumentContextBuilder {
-        add(ParserPair(this, object : CommandArgumentParser<T> {
+        add(ParserPair(this, object : CommandValueArgumentParser<T> {
            override fun parse(raw: String, sender: CommandSender): T = parser(raw)
        }))
        return this@CommandArgumentContextBuilder
    }

    @JvmSynthetic
-    public inline fun <reified T : Any> add(parser: CommandArgumentParser<T>): CommandArgumentContextBuilder {
+    public inline fun <reified T : Any> add(parser: CommandValueArgumentParser<T>): CommandArgumentContextBuilder {
        add(ParserPair(T::class, parser))
        return this@CommandArgumentContextBuilder
    }
@ -251,8 +254,8 @@ public class CommandArgumentContextBuilder : MutableList<ParserPair<*>> by mutab
    @ConsoleExperimentalApi
    @JvmSynthetic
    public inline infix fun <reified T : Any> add(
-        crossinline parser: CommandArgumentParser<*>.(s: String) -> T,
-    ): CommandArgumentContextBuilder = T::class with object : CommandArgumentParser<T> {
+        crossinline parser: CommandValueArgumentParser<*>.(s: String) -> T,
+    ): CommandArgumentContextBuilder = T::class with object : CommandValueArgumentParser<T> {
        override fun parse(raw: String, sender: CommandSender): T = parser(raw)
    }

@ -263,8 +266,8 @@ public class CommandArgumentContextBuilder : MutableList<ParserPair<*>> by mutab
    @JvmSynthetic
    @LowPriorityInOverloadResolution
    public inline infix fun <reified T : Any> add(
-        crossinline parser: CommandArgumentParser<*>.(s: String, sender: CommandSender) -> T,
-    ): CommandArgumentContextBuilder = T::class with object : CommandArgumentParser<T> {
+        crossinline parser: CommandValueArgumentParser<*>.(s: String, sender: CommandSender) -> T,
+    ): CommandArgumentContextBuilder = T::class with object : CommandValueArgumentParser<T> {
        override fun parse(raw: String, sender: CommandSender): T = parser(raw, sender)
    }

--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentParserBuiltins.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentParserBuiltins.kt
@ -7,7 +7,7 @@
 * https://github.com/mamoe/mirai/blob/master/LICENSE
 */

-package net.mamoe.mirai.console.command.description
+package net.mamoe.mirai.console.command.descriptor

 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.console.command.*
@ -25,47 +25,47 @@ import net.mamoe.mirai.message.data.*
 /**
 * 使用 [String.toInt] 解析
 */
-public object IntArgumentParser : InternalCommandArgumentParserExtensions<Int> {
+public object IntValueArgumentParser : InternalCommandValueArgumentParserExtensions<Int> {
    public override fun parse(raw: String, sender: CommandSender): Int =
        raw.toIntOrNull() ?: illegalArgument("无法解析 $raw 为整数")
 }

 /**
- * 使用 [String.toInt] 解析
+ * 使用 [String.toLong] 解析
 */
-public object LongArgumentParser : InternalCommandArgumentParserExtensions<Long> {
+public object LongValueArgumentParser : InternalCommandValueArgumentParserExtensions<Long> {
    public override fun parse(raw: String, sender: CommandSender): Long =
        raw.toLongOrNull() ?: illegalArgument("无法解析 $raw 为长整数")
 }

 /**
- * 使用 [String.toInt] 解析
+ * 使用 [String.toShort] 解析
 */
-public object ShortArgumentParser : InternalCommandArgumentParserExtensions<Short> {
+public object ShortValueArgumentParser : InternalCommandValueArgumentParserExtensions<Short> {
    public override fun parse(raw: String, sender: CommandSender): Short =
        raw.toShortOrNull() ?: illegalArgument("无法解析 $raw 为短整数")
 }

 /**
- * 使用 [String.toInt] 解析
+ * 使用 [String.toByte] 解析
 */
-public object ByteArgumentParser : InternalCommandArgumentParserExtensions<Byte> {
+public object ByteValueArgumentParser : InternalCommandValueArgumentParserExtensions<Byte> {
    public override fun parse(raw: String, sender: CommandSender): Byte =
        raw.toByteOrNull() ?: illegalArgument("无法解析 $raw 为字节")
 }

 /**
- * 使用 [String.toInt] 解析
+ * 使用 [String.toDouble] 解析
 */
-public object DoubleArgumentParser : InternalCommandArgumentParserExtensions<Double> {
+public object DoubleValueArgumentParser : InternalCommandValueArgumentParserExtensions<Double> {
    public override fun parse(raw: String, sender: CommandSender): Double =
        raw.toDoubleOrNull() ?: illegalArgument("无法解析 $raw 为小数")
 }

 /**
- * 使用 [String.toInt] 解析
+ * 使用 [String.toFloat] 解析
 */
-public object FloatArgumentParser : InternalCommandArgumentParserExtensions<Float> {
+public object FloatValueArgumentParser : InternalCommandValueArgumentParserExtensions<Float> {
    public override fun parse(raw: String, sender: CommandSender): Float =
        raw.toFloatOrNull() ?: illegalArgument("无法解析 $raw 为小数")
 }
@ -73,14 +73,14 @@ public object FloatArgumentParser : InternalCommandArgumentParserExtensions<Floa
 /**
 * 直接返回 [String], 或取用 [SingleMessage.contentToString]
 */
-public object StringArgumentParser : InternalCommandArgumentParserExtensions<String> {
+public object StringValueArgumentParser : InternalCommandValueArgumentParserExtensions<String> {
    public override fun parse(raw: String, sender: CommandSender): String = raw
 }

 /**
 * 解析 [String] 通过 [Image].
 */
-public object ImageArgumentParser : InternalCommandArgumentParserExtensions<Image> {
+public object ImageValueArgumentParser : InternalCommandValueArgumentParserExtensions<Image> {
    public override fun parse(raw: String, sender: CommandSender): Image {
        return kotlin.runCatching {
            Image(raw)
@ -95,7 +95,7 @@ public object ImageArgumentParser : InternalCommandArgumentParserExtensions<Imag
    }
 }

-public object PlainTextArgumentParser : InternalCommandArgumentParserExtensions<PlainText> {
+public object PlainTextValueArgumentParser : InternalCommandValueArgumentParserExtensions<PlainText> {
    public override fun parse(raw: String, sender: CommandSender): PlainText {
        return PlainText(raw)
    }
@ -109,7 +109,7 @@ public object PlainTextArgumentParser : InternalCommandArgumentParserExtensions<
 /**
 * 当字符串内容为(不区分大小写) "true", "yes", "enabled"
 */
-public object BooleanArgumentParser : InternalCommandArgumentParserExtensions<Boolean> {
+public object BooleanValueArgumentParser : InternalCommandValueArgumentParserExtensions<Boolean> {
    public override fun parse(raw: String, sender: CommandSender): Boolean = raw.trim().let { str ->
        str.equals("true", ignoreCase = true)
            || str.equals("yes", ignoreCase = true)
@ -121,7 +121,7 @@ public object BooleanArgumentParser : InternalCommandArgumentParserExtensions<Bo
 /**
 * 根据 [Bot.id] 解析一个登录后的 [Bot]
 */
-public object ExistingBotArgumentParser : InternalCommandArgumentParserExtensions<Bot> {
+public object ExistingBotValueArgumentParser : InternalCommandValueArgumentParserExtensions<Bot> {
    public override fun parse(raw: String, sender: CommandSender): Bot =
        if (raw == "~") sender.inferBotOrFail()
        else raw.findBotOrFail()
@ -136,7 +136,7 @@ public object ExistingBotArgumentParser : InternalCommandArgumentParserExtension
 /**
 * 解析任意一个存在的好友.
 */
-public object ExistingFriendArgumentParser : InternalCommandArgumentParserExtensions<Friend> {
+public object ExistingFriendValueArgumentParser : InternalCommandValueArgumentParserExtensions<Friend> {
    private val syntax = """
        - `botId.friendId`
        - `botId.friendNick` (模糊搜索, 寻找最优匹配)
@ -175,7 +175,7 @@ public object ExistingFriendArgumentParser : InternalCommandArgumentParserExtens
 /**
 * 解析任意一个存在的群.
 */
-public object ExistingGroupArgumentParser : InternalCommandArgumentParserExtensions<Group> {
+public object ExistingGroupValueArgumentParser : InternalCommandValueArgumentParserExtensions<Group> {
    private val syntax = """
        - `botId.groupId`
        - `~` (指代指令调用人自己所在群. 仅群聊天环境下)
@ -202,7 +202,7 @@ public object ExistingGroupArgumentParser : InternalCommandArgumentParserExtensi
    }
 }

-public object ExistingUserArgumentParser : InternalCommandArgumentParserExtensions<User> {
+public object ExistingUserValueArgumentParser : InternalCommandValueArgumentParserExtensions<User> {
    private val syntax: String = """
         - `botId.groupId.memberId`
         - `botId.groupId.memberCard` (模糊搜索, 寻找最优匹配)
@ -215,11 +215,11 @@ public object ExistingUserArgumentParser : InternalCommandArgumentParserExtensio
    """.trimIndent()

    override fun parse(raw: String, sender: CommandSender): User {
-        return parseImpl(sender, raw, ExistingMemberArgumentParser::parse, ExistingFriendArgumentParser::parse)
+        return parseImpl(sender, raw, ExistingMemberValueArgumentParser::parse, ExistingFriendValueArgumentParser::parse)
    }

    override fun parse(raw: MessageContent, sender: CommandSender): User {
-        return parseImpl(sender, raw, ExistingMemberArgumentParser::parse, ExistingFriendArgumentParser::parse)
+        return parseImpl(sender, raw, ExistingMemberValueArgumentParser::parse, ExistingFriendValueArgumentParser::parse)
    }

    private fun <T> parseImpl(
@ -246,7 +246,7 @@ public object ExistingUserArgumentParser : InternalCommandArgumentParserExtensio
 }


-public object ExistingContactArgumentParser : InternalCommandArgumentParserExtensions<Contact> {
+public object ExistingContactValueArgumentParser : InternalCommandValueArgumentParserExtensions<Contact> {
    private val syntax: String = """
         - `botId.groupId.memberId`
         - `botId.groupId.memberCard` (模糊搜索, 寻找最优匹配)
@ -259,11 +259,11 @@ public object ExistingContactArgumentParser : InternalCommandArgumentParserExten
    """.trimIndent()

    override fun parse(raw: String, sender: CommandSender): Contact {
-        return parseImpl(sender, raw, ExistingUserArgumentParser::parse, ExistingGroupArgumentParser::parse)
+        return parseImpl(sender, raw, ExistingUserValueArgumentParser::parse, ExistingGroupValueArgumentParser::parse)
    }

    override fun parse(raw: MessageContent, sender: CommandSender): Contact {
-        return parseImpl(sender, raw, ExistingUserArgumentParser::parse, ExistingGroupArgumentParser::parse)
+        return parseImpl(sender, raw, ExistingUserValueArgumentParser::parse, ExistingGroupValueArgumentParser::parse)
    }

    private fun <T> parseImpl(
@ -286,7 +286,7 @@ public object ExistingContactArgumentParser : InternalCommandArgumentParserExten
 /**
 * 解析任意一个群成员.
 */
-public object ExistingMemberArgumentParser : InternalCommandArgumentParserExtensions<Member> {
+public object ExistingMemberValueArgumentParser : InternalCommandValueArgumentParserExtensions<Member> {
    private val syntax: String = """
         - `botId.groupId.memberId`
         - `botId.groupId.memberCard` (模糊搜索, 寻找最优匹配)
@ -333,7 +333,7 @@ public object ExistingMemberArgumentParser : InternalCommandArgumentParserExtens
    }
 }

-public object PermissionIdArgumentParser : CommandArgumentParser<PermissionId> {
+public object PermissionIdValueArgumentParser : CommandValueArgumentParser<PermissionId> {
    override fun parse(raw: String, sender: CommandSender): PermissionId {
        return kotlin.runCatching { PermissionId.parseFromString(raw) }.getOrElse {
            illegalArgument("无法解析 $raw 为 PermissionId")
@ -341,7 +341,7 @@ public object PermissionIdArgumentParser : CommandArgumentParser<PermissionId> {
    }
 }

-public object PermitteeIdArgumentParser : CommandArgumentParser<PermitteeId> {
+public object PermitteeIdValueArgumentParser : CommandValueArgumentParser<PermitteeId> {
    override fun parse(raw: String, sender: CommandSender): PermitteeId {
        return if (raw == "~") sender.permitteeId
        else kotlin.runCatching { AbstractPermitteeId.parseFromString(raw) }.getOrElse {
@ -351,13 +351,19 @@ public object PermitteeIdArgumentParser : CommandArgumentParser<PermitteeId> {

    override fun parse(raw: MessageContent, sender: CommandSender): PermitteeId {
        if (raw is At) {
-            return ExistingUserArgumentParser.parse(raw, sender).asCommandSender(false).permitteeId
+            return ExistingUserValueArgumentParser.parse(raw, sender).asCommandSender(false).permitteeId
        }
        return super.parse(raw, sender)
    }
 }

-internal interface InternalCommandArgumentParserExtensions<T : Any> : CommandArgumentParser<T> {
+/** 直接返回原始参数 [MessageContent] */
+public object RawContentValueArgumentParser : CommandValueArgumentParser<MessageContent> {
+    override fun parse(raw: String, sender: CommandSender): MessageContent = PlainText(raw)
+    override fun parse(raw: MessageContent, sender: CommandSender): MessageContent = raw
+}
+
+internal interface InternalCommandValueArgumentParserExtensions<T : Any> : CommandValueArgumentParser<T> {
    fun String.parseToLongOrFail(): Long = toLongOrNull() ?: illegalArgument("无法解析 $this 为整数")

    fun Long.findBotOrFail(): Bot = Bot.getInstanceOrNull(this) ?: illegalArgument("无法找到 Bot: $this")
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentParserException.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentParserException.kt
@ -9,17 +9,20 @@

@file:Suppress("unused")

-package net.mamoe.mirai.console.command.description
+package net.mamoe.mirai.console.command.descriptor
+
+import net.mamoe.mirai.console.command.IllegalCommandArgumentException

 /**
 * 在解析参数时遇到的 _正常_ 错误. 如参数不符合规范等.
 *
 * [message] 将会发送给指令调用方.
 *
- * @see CommandArgumentParser
- * @see CommandArgumentParser.illegalArgument
+ * @see IllegalCommandArgumentException
+ * @see CommandValueArgumentParser
+ * @see CommandValueArgumentParser.illegalArgument
 */
-public class CommandArgumentParserException : RuntimeException {
+public class CommandArgumentParserException : IllegalCommandArgumentException {
    public constructor() : super()
    public constructor(message: String?) : super(message)
    public constructor(message: String?, cause: Throwable?) : super(message, cause)
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandDescriptor.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandDescriptor.kt
@ -0,0 +1,287 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.command.descriptor
+
+import net.mamoe.mirai.console.command.CommandSender
+import net.mamoe.mirai.console.command.descriptor.AbstractCommandValueParameter.UserDefinedType.Companion.createOptional
+import net.mamoe.mirai.console.command.descriptor.AbstractCommandValueParameter.UserDefinedType.Companion.createRequired
+import net.mamoe.mirai.console.command.descriptor.ArgumentAcceptance.Companion.isAcceptable
+import net.mamoe.mirai.console.command.parse.CommandValueArgument
+import net.mamoe.mirai.console.command.resolve.ResolvedCommandCall
+import net.mamoe.mirai.console.internal.data.classifierAsKClass
+import net.mamoe.mirai.console.internal.data.classifierAsKClassOrNull
+import net.mamoe.mirai.console.internal.data.typeOf0
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import kotlin.reflect.KClass
+import kotlin.reflect.KFunction
+import kotlin.reflect.KType
+import kotlin.reflect.full.isSubtypeOf
+import kotlin.reflect.typeOf
+
+/**
+ * @see CommandSignatureVariantImpl
+ */
+@ExperimentalCommandDescriptors
+public interface CommandSignatureVariant {
+    @ConsoleExperimentalApi
+    public val receiverParameter: CommandReceiverParameter<out CommandSender>?
+
+    public val valueParameters: List<AbstractCommandValueParameter<*>>
+
+    public suspend fun call(resolvedCommandCall: ResolvedCommandCall)
+}
+
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public interface CommandSignatureVariantFromKFunction : CommandSignatureVariant {
+    public val originFunction: KFunction<*>
+}
+
+@ExperimentalCommandDescriptors
+public abstract class AbstractCommandSignatureVariant : CommandSignatureVariant {
+    override fun toString(): String {
+        val receiverParameter = receiverParameter
+        return if (receiverParameter == null) {
+            "CommandSignatureVariant(${valueParameters.joinToString()})"
+        } else {
+            "CommandSignatureVariant($receiverParameter, ${valueParameters.joinToString()})"
+        }
+    }
+}
+
+@ExperimentalCommandDescriptors
+public open class CommandSignatureVariantImpl(
+    override val receiverParameter: CommandReceiverParameter<out CommandSender>?,
+    override val valueParameters: List<AbstractCommandValueParameter<*>>,
+    private val onCall: suspend CommandSignatureVariantImpl.(resolvedCommandCall: ResolvedCommandCall) -> Unit,
+) : CommandSignatureVariant, AbstractCommandSignatureVariant() {
+    override suspend fun call(resolvedCommandCall: ResolvedCommandCall) {
+        return onCall(resolvedCommandCall)
+    }
+}
+
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public open class CommandSignatureVariantFromKFunctionImpl(
+    override val receiverParameter: CommandReceiverParameter<out CommandSender>?,
+    override val valueParameters: List<AbstractCommandValueParameter<*>>,
+    override val originFunction: KFunction<*>,
+    private val onCall: suspend CommandSignatureVariantFromKFunctionImpl.(resolvedCommandCall: ResolvedCommandCall) -> Unit,
+) : CommandSignatureVariantFromKFunction, AbstractCommandSignatureVariant() {
+    override suspend fun call(resolvedCommandCall: ResolvedCommandCall) {
+        return onCall(resolvedCommandCall)
+    }
+}
+
+
+/**
+ * Inherited instances must be [CommandValueParameter] or [CommandReceiverParameter]
+ */
+@ExperimentalCommandDescriptors
+public interface CommandParameter<T : Any?> {
+    public val name: String?
+
+    public val isOptional: Boolean
+
+    /**
+     * Reified type of [T]
+     */
+    public val type: KType
+}
+
+@ExperimentalCommandDescriptors
+public abstract class AbstractCommandParameter<T> : CommandParameter<T> {
+    override fun toString(): String = buildString {
+        append(name)
+        append(": ")
+        append(type.classifierAsKClass().simpleName)
+        append(if (type.isMarkedNullable) "?" else "")
+    }
+}
+
+/**
+ * Inherited instances must be [AbstractCommandValueParameter]
+ */
+@ExperimentalCommandDescriptors
+public interface CommandValueParameter<T : Any?> : CommandParameter<T> {
+
+    public val isVararg: Boolean
+
+    public fun accepts(argument: CommandValueArgument, commandArgumentContext: CommandArgumentContext?): Boolean =
+        accepting(argument, commandArgumentContext).isAcceptable
+
+    public fun accepting(argument: CommandValueArgument, commandArgumentContext: CommandArgumentContext?): ArgumentAcceptance
+}
+
+@ExperimentalCommandDescriptors
+public sealed class ArgumentAcceptance(
+    /**
+     * Higher means more acceptable
+     */
+    @ConsoleExperimentalApi
+    public val acceptanceLevel: Int,
+) {
+    public object Direct : ArgumentAcceptance(Int.MAX_VALUE)
+
+    public class WithTypeConversion(
+        public val typeVariant: TypeVariant<*>,
+    ) : ArgumentAcceptance(20)
+
+    public class WithContextualConversion(
+        public val parser: CommandValueArgumentParser<*>,
+    ) : ArgumentAcceptance(10)
+
+    public class ResolutionAmbiguity(
+        public val candidates: List<TypeVariant<*>>,
+    ) : ArgumentAcceptance(0)
+
+    public object Impossible : ArgumentAcceptance(-1)
+
+    public companion object {
+        @JvmStatic
+        public val ArgumentAcceptance.isAcceptable: Boolean
+            get() = acceptanceLevel > 0
+
+        @JvmStatic
+        public val ArgumentAcceptance.isNotAcceptable: Boolean
+            get() = acceptanceLevel <= 0
+    }
+}
+
+@ExperimentalCommandDescriptors
+public class CommandReceiverParameter<T : CommandSender>(
+    override val isOptional: Boolean,
+    override val type: KType,
+) : CommandParameter<T>, AbstractCommandParameter<T>() {
+    override val name: String get() = PARAMETER_NAME
+
+    init {
+        check(type.classifier is KClass<*>) {
+            "CommandReceiverParameter.type.classifier must be KClass."
+        }
+    }
+
+    public companion object {
+        public const val PARAMETER_NAME: String = "<receiver>"
+    }
+}
+
+
+internal val ANY_TYPE = typeOf0<Any>()
+internal val ARRAY_OUT_ANY_TYPE = typeOf0<Array<out Any?>>()
+
+@ExperimentalCommandDescriptors
+public sealed class AbstractCommandValueParameter<T> : CommandValueParameter<T>, AbstractCommandParameter<T>() {
+    override fun toString(): String = buildString {
+        if (isVararg) append("vararg ")
+        append(super.toString())
+        if (isOptional) {
+            append(" = ...")
+        }
+    }
+
+    public override fun accepting(argument: CommandValueArgument, commandArgumentContext: CommandArgumentContext?): ArgumentAcceptance {
+        if (isVararg) {
+            val arrayElementType = this.type.arguments.single() // Array<T>
+            return acceptingImpl(arrayElementType.type ?: ANY_TYPE, argument, commandArgumentContext)
+        }
+
+        return acceptingImpl(this.type, argument, commandArgumentContext)
+    }
+
+    private fun acceptingImpl(
+        expectingType: KType,
+        argument: CommandValueArgument,
+        commandArgumentContext: CommandArgumentContext?,
+    ): ArgumentAcceptance {
+        if (argument.type.isSubtypeOf(expectingType)) return ArgumentAcceptance.Direct
+
+        argument.typeVariants.associateWith { typeVariant ->
+            if (typeVariant.outType.isSubtypeOf(expectingType)) {
+                // TODO: 2020/10/11 resolution ambiguity
+                return ArgumentAcceptance.WithTypeConversion(typeVariant)
+            }
+        }
+        expectingType.classifierAsKClassOrNull()?.let { commandArgumentContext?.get(it) }?.let { parser ->
+            return ArgumentAcceptance.WithContextualConversion(parser)
+        }
+        return ArgumentAcceptance.Impossible
+    }
+
+    @ConsoleExperimentalApi
+    public class StringConstant(
+        @ConsoleExperimentalApi
+        public override val name: String?,
+        public val expectingValue: String,
+    ) : AbstractCommandValueParameter<String>() {
+        public override val type: KType get() = STRING_TYPE
+        public override val isOptional: Boolean get() = false
+        public override val isVararg: Boolean get() = false
+
+        init {
+            require(expectingValue.isNotBlank()) {
+                "expectingValue must not be blank"
+            }
+            require(expectingValue.none(Char::isWhitespace)) {
+                "expectingValue must not contain whitespace"
+            }
+        }
+
+        override fun toString(): String = "<$expectingValue>"
+
+        private companion object {
+            @OptIn(ExperimentalStdlibApi::class)
+            val STRING_TYPE = typeOf<String>()
+        }
+    }
+
+    /**
+     * @see createOptional
+     * @see createRequired
+     */
+    public class UserDefinedType<T>(
+        public override val name: String?,
+        public override val isOptional: Boolean,
+        public override val isVararg: Boolean,
+        public override val type: KType,
+    ) : AbstractCommandValueParameter<T>() {
+        init {
+            requireNotNull(type.classifierAsKClassOrNull()) {
+                "type.classifier must be KClass."
+            }
+            if (isVararg)
+                check(type.isSubtypeOf(ARRAY_OUT_ANY_TYPE)) {
+                    "type must be subtype of Array if vararg. Given $type."
+                }
+        }
+
+        public companion object {
+            @JvmStatic
+            public inline fun <reified T : Any> createOptional(name: String, isVararg: Boolean): UserDefinedType<T> {
+                @OptIn(ExperimentalStdlibApi::class)
+                return UserDefinedType(name, true, isVararg, typeOf<T>())
+            }
+
+            @JvmStatic
+            public inline fun <reified T : Any> createRequired(name: String, isVararg: Boolean): UserDefinedType<T> {
+                @OptIn(ExperimentalStdlibApi::class)
+                return UserDefinedType(name, false, isVararg, typeOf<T>())
+            }
+        }
+    }
+
+    /**
+     * Extended by [CommandValueArgumentParser]
+     */
+    @ConsoleExperimentalApi
+    public abstract class Extended<T> : AbstractCommandValueParameter<T>() {
+        abstract override fun toString(): String
+    }
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandValueArgumentParser.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandValueArgumentParser.kt
@ -9,7 +9,7 @@

@file:Suppress("NOTHING_TO_INLINE", "unused")

-package net.mamoe.mirai.console.command.description
+package net.mamoe.mirai.console.command.descriptor

 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.console.command.CommandManager
@ -32,27 +32,27 @@ import kotlin.contracts.contract
 * ```
 * suspend fun CommandSender.mute(target: Member, duration: Int)
 * ```
- * [CommandManager] 总是从 [SimpleCommand.context] 搜索一个 [T] 为 [Member] 的 [CommandArgumentParser], 并调用其 [CommandArgumentParser.parse]
+ * [CommandManager] 总是从 [SimpleCommand.context] 搜索一个 [T] 为 [Member] 的 [CommandValueArgumentParser], 并调用其 [CommandValueArgumentParser.parse]
 *
 * ### 内建指令解析器
- * - 基础类型: [ByteArgumentParser], [ShortArgumentParser], [IntArgumentParser], [LongArgumentParser]
- * [FloatArgumentParser], [DoubleArgumentParser],
- * [BooleanArgumentParser], [StringArgumentParser]
+ * - 基础类型: [ByteValueArgumentParser], [ShortValueArgumentParser], [IntValueArgumentParser], [LongValueArgumentParser]
+ * [FloatValueArgumentParser], [DoubleValueArgumentParser],
+ * [BooleanValueArgumentParser], [StringValueArgumentParser]
 *
- * - [Bot]: [ExistingBotArgumentParser]
- * - [Friend]: [ExistingFriendArgumentParser]
- * - [Group]: [ExistingGroupArgumentParser]
- * - [Member]: [ExistingMemberArgumentParser]
- * - [User]: [ExistingUserArgumentParser]
- * - [Contact]: [ExistingContactArgumentParser]
+ * - [Bot]: [ExistingBotValueArgumentParser]
+ * - [Friend]: [ExistingFriendValueArgumentParser]
+ * - [Group]: [ExistingGroupValueArgumentParser]
+ * - [Member]: [ExistingMemberValueArgumentParser]
+ * - [User]: [ExistingUserValueArgumentParser]
+ * - [Contact]: [ExistingContactValueArgumentParser]
 *
 *
 * @see SimpleCommand 简单指令
 * @see CompositeCommand 复合指令
 *
- * @see buildCommandArgumentContext 指令参数环境, 即 [CommandArgumentParser] 的集合
+ * @see buildCommandArgumentContext 指令参数环境, 即 [CommandValueArgumentParser] 的集合
 */
-public interface CommandArgumentParser<out T : Any> {
+public interface CommandValueArgumentParser<out T : Any> {
    /**
     * 解析一个字符串为 [T] 类型参数
     *
@ -83,14 +83,14 @@ public interface CommandArgumentParser<out T : Any> {
 /**
 * 使用原 [this] 解析, 成功后使用 [mapper] 映射为另一个类型.
 */
-public fun <T : Any, R : Any> CommandArgumentParser<T>.map(
-    mapper: CommandArgumentParser<R>.(T) -> R
-): CommandArgumentParser<R> = MappingCommandArgumentParser(this, mapper)
+public fun <T : Any, R : Any> CommandValueArgumentParser<T>.map(
+    mapper: CommandValueArgumentParser<R>.(T) -> R,
+): CommandValueArgumentParser<R> = MappingCommandValueArgumentParser(this, mapper)

-private class MappingCommandArgumentParser<T : Any, R : Any>(
-    private val original: CommandArgumentParser<T>,
-    private val mapper: CommandArgumentParser<R>.(T) -> R
-) : CommandArgumentParser<R> {
+private class MappingCommandValueArgumentParser<T : Any, R : Any>(
+    private val original: CommandValueArgumentParser<T>,
+    private val mapper: CommandValueArgumentParser<R>.(T) -> R,
+) : CommandValueArgumentParser<R> {
    override fun parse(raw: String, sender: CommandSender): R = mapper(original.parse(raw, sender))
    override fun parse(raw: MessageContent, sender: CommandSender): R = mapper(original.parse(raw, sender))
 }
@ -102,14 +102,14 @@ private class MappingCommandArgumentParser<T : Any, R : Any>(
 */
@JvmSynthetic
@Throws(IllegalArgumentException::class)
-public fun <T : Any> CommandArgumentParser<T>.parse(raw: Any, sender: CommandSender): T {
+public fun <T : Any> CommandValueArgumentParser<T>.parse(raw: Any, sender: CommandSender): T {
    contract {
        returns() implies (raw is String || raw is SingleMessage)
    }

    return when (raw) {
        is String -> parse(raw, sender)
-        is SingleMessage -> parse(raw, sender)
+        is MessageContent -> parse(raw, sender)
        else -> throw IllegalArgumentException("Illegal raw argument type: ${raw::class.qualifiedName}")
    }
 }
@ -122,7 +122,7 @@ public fun <T : Any> CommandArgumentParser<T>.parse(raw: Any, sender: CommandSen
@Suppress("unused")
@JvmSynthetic
@Throws(CommandArgumentParserException::class)
-public inline fun CommandArgumentParser<*>.illegalArgument(message: String, cause: Throwable? = null): Nothing {
+public inline fun CommandValueArgumentParser<*>.illegalArgument(message: String, cause: Throwable? = null): Nothing {
    throw CommandArgumentParserException(message, cause)
 }

@ -133,9 +133,9 @@ public inline fun CommandArgumentParser<*>.illegalArgument(message: String, caus
 */
@Throws(CommandArgumentParserException::class)
@JvmSynthetic
-public inline fun CommandArgumentParser<*>.checkArgument(
+public inline fun CommandValueArgumentParser<*>.checkArgument(
    condition: Boolean,
-    crossinline message: () -> String = { "Check failed." }
+    crossinline message: () -> String = { "Check failed." },
 ) {
    contract {
        returns() implies condition
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/Exceptions.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/Exceptions.kt
@ -0,0 +1,40 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:Suppress("MemberVisibilityCanBePrivate", "unused")
+
+package net.mamoe.mirai.console.command.descriptor
+
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.command.parse.CommandValueArgument
+import net.mamoe.mirai.console.internal.data.classifierAsKClassOrNull
+import net.mamoe.mirai.console.internal.data.qualifiedNameOrTip
+import kotlin.reflect.KType
+
+
+internal val KType.qualifiedName: String
+    get() = this.classifierAsKClassOrNull()?.qualifiedNameOrTip ?: classifier.toString()
+
+@ExperimentalCommandDescriptors
+public open class NoValueArgumentMappingException(
+    public val argument: CommandValueArgument,
+    public val forType: KType,
+) : CommandResolutionException("Cannot find a CommandArgument mapping for ${forType.qualifiedName}")
+
+@ExperimentalCommandDescriptors
+public open class UnresolvedCommandCallException(
+    public val call: CommandCall,
+) : CommandResolutionException("Unresolved call: $call")
+
+public open class CommandResolutionException : RuntimeException {
+    public constructor() : super()
+    public constructor(message: String?) : super(message)
+    public constructor(message: String?, cause: Throwable?) : super(message, cause)
+    public constructor(cause: Throwable?) : super(cause)
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/ExperimentalCommandDescriptors.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/ExperimentalCommandDescriptors.kt
@ -0,0 +1,31 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.command.descriptor
+
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import kotlin.annotation.AnnotationTarget.*
+
+/**
+ * 标记一个实验性的指令解释器 API.
+ *
+ * 这些 API 不具有稳定性, 且可能会在任意时刻更改.
+ * 不建议在发行版本中使用这些 API.
+ *
+ * @since 1.0-RC
+ */
+@Retention(AnnotationRetention.BINARY)
+@RequiresOptIn(level = RequiresOptIn.Level.WARNING)
+@Target(CLASS, TYPEALIAS, FUNCTION, PROPERTY, FIELD, CONSTRUCTOR)
+@MustBeDocumented
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public annotation class ExperimentalCommandDescriptors(
+    val message: String = "Command descriptors are an experimental API.",
+)
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/TypeVariant.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/TypeVariant.kt
@ -0,0 +1,70 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.command.descriptor
+
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.command.parse.CommandCallParser
+import net.mamoe.mirai.console.command.parse.CommandValueArgument
+import net.mamoe.mirai.console.internal.data.castOrNull
+import net.mamoe.mirai.console.internal.data.kClassQualifiedName
+import net.mamoe.mirai.message.data.*
+import kotlin.reflect.KType
+import kotlin.reflect.typeOf
+
+/**
+ * Implicit type variant specified by [CommandCallParser].
+ *
+ * [TypeVariant] is not necessary for all [CommandCall]s.
+ */
+@ExperimentalCommandDescriptors
+public interface TypeVariant<out OutType> {
+    /**
+     * The reified type of [OutType]
+     */
+    public val outType: KType
+
+    /**
+     * @see CommandValueArgument.value
+     */
+    public fun mapValue(valueParameter: Message): OutType
+
+    public companion object {
+        @OptIn(ExperimentalStdlibApi::class)
+        @JvmSynthetic
+        public inline operator fun <reified OutType> invoke(crossinline block: (valueParameter: Message) -> OutType): TypeVariant<OutType> {
+            return object : TypeVariant<OutType> {
+                override val outType: KType = typeOf<OutType>()
+                override fun mapValue(valueParameter: Message): OutType = block(valueParameter)
+            }
+        }
+    }
+}
+
+@ExperimentalCommandDescriptors
+public object MessageContentTypeVariant : TypeVariant<MessageContent> {
+    @OptIn(ExperimentalStdlibApi::class)
+    override val outType: KType = typeOf<MessageContent>()
+    override fun mapValue(valueParameter: Message): MessageContent =
+        valueParameter.castOrNull<MessageContent>() ?: error("Accepts MessageContent only but given ${valueParameter.kClassQualifiedName}")
+}
+
+@ExperimentalCommandDescriptors
+public object MessageChainTypeVariant : TypeVariant<MessageChain> {
+    @OptIn(ExperimentalStdlibApi::class)
+    override val outType: KType = typeOf<MessageChain>()
+    override fun mapValue(valueParameter: Message): MessageChain = valueParameter.asMessageChain()
+}
+
+@ExperimentalCommandDescriptors
+public object ContentStringTypeVariant : TypeVariant<String> {
+    @OptIn(ExperimentalStdlibApi::class)
+    override val outType: KType = typeOf<String>()
+    override fun mapValue(valueParameter: Message): String = valueParameter.content
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JCommand.kt
@ -9,13 +9,8 @@

 package net.mamoe.mirai.console.command.java

-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.withContext
 import net.mamoe.mirai.console.command.Command
-import net.mamoe.mirai.console.command.CommandManager
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
-import net.mamoe.mirai.console.command.CommandSender
-import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi

 /**
 * 为 Java 用户添加协程帮助的 [Command].
@ -24,17 +19,7 @@ import net.mamoe.mirai.message.data.MessageChain
 *
 * @see Command
 */
+@ConsoleExperimentalApi("Not yet supported")
 public interface JCommand : Command {
-    public override suspend fun CommandSender.onCommand(args: MessageChain) {
-        withContext(Dispatchers.IO) { onCommand(this@onCommand, args) }
-    }
-
-    /**
-     * 在指令被执行时调用.
-     *
-     * @param args 精确的指令参数. [MessageChain] 每个元素代表一个精确的参数.
-     *
-     * @see CommandManager.executeCommand 查看更多信息
-     */
-    public fun onCommand(sender: CommandSender, args: MessageChain) // overrides blocking bridge
+    // TODO: 2020/10/18 JCommand
 }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JCompositeCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JCompositeCommand.kt
@ -13,10 +13,11 @@ import net.mamoe.mirai.console.command.BuiltInCommands
 import net.mamoe.mirai.console.command.CommandManager
 import net.mamoe.mirai.console.command.CommandOwner
 import net.mamoe.mirai.console.command.CompositeCommand
-import net.mamoe.mirai.console.command.description.buildCommandArgumentContext
+import net.mamoe.mirai.console.command.descriptor.buildCommandArgumentContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
 import net.mamoe.mirai.console.permission.Permission
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi

 /**
 * 复合指令. 指令注册时候会通过反射构造指令解析器.
@ -68,6 +69,7 @@ import net.mamoe.mirai.console.permission.Permission
 *
 * @see buildCommandArgumentContext
 */
+@ConsoleExperimentalApi("Not yet supported")
 public abstract class JCompositeCommand
@JvmOverloads constructor(
    owner: CommandOwner,
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JRawCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JRawCommand.kt
@ -9,16 +9,15 @@

 package net.mamoe.mirai.console.command.java

-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.withContext
-import net.mamoe.mirai.console.command.*
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.execute
+import net.mamoe.mirai.console.command.BuiltInCommands
+import net.mamoe.mirai.console.command.Command
+import net.mamoe.mirai.console.command.CommandManager
+import net.mamoe.mirai.console.command.CommandOwner
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
 import net.mamoe.mirai.console.internal.command.createOrFindCommandPermission
 import net.mamoe.mirai.console.permission.Permission
-import net.mamoe.mirai.message.data.MessageChain
-import net.mamoe.mirai.message.data.SingleMessage
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi

 /**
 * 供 Java 用户继承
@ -46,6 +45,7 @@ import net.mamoe.mirai.message.data.SingleMessage
 *
 * @see JRawCommand
 */
+@ConsoleExperimentalApi("Not yet supported")
 public abstract class JRawCommand
@JvmOverloads constructor(
    /**
@ -72,19 +72,4 @@ public abstract class JRawCommand
    /** 为 `true` 时表示 [指令前缀][CommandManager.commandPrefix] 可选 */
    public final override var prefixOptional: Boolean = false
        protected set
-
-    /**
-     * 在指令被执行时调用.
-     *
-     * @param args 指令参数. 数组元素类型可能是 [SingleMessage] 或 [String]. 且已经以 ' ' 分割.
-     *
-     * @see CommandManager.execute 查看更多信息
-     */
-    @Suppress("INAPPLICABLE_JVM_NAME")
-    @JvmName("onCommand")
-    public abstract fun onCommand(sender: CommandSender, args: MessageChain)
-
-    public final override suspend fun CommandSender.onCommand(args: MessageChain) {
-        withContext(Dispatchers.IO) { onCommand(this@onCommand, args) }
-    }
 }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JSimpleCommand.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/java/JSimpleCommand.kt
@ -13,10 +13,11 @@ import net.mamoe.mirai.console.command.CommandManager
 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
 import net.mamoe.mirai.console.command.CommandOwner
 import net.mamoe.mirai.console.command.SimpleCommand
-import net.mamoe.mirai.console.command.description.CommandArgumentContext
+import net.mamoe.mirai.console.command.descriptor.CommandArgumentContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext
 import net.mamoe.mirai.console.compiler.common.ResolveContext.Kind.COMMAND_NAME
 import net.mamoe.mirai.console.permission.Permission
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi

 /**
 * Java 实现:
@ -42,6 +43,7 @@ import net.mamoe.mirai.console.permission.Permission
 * @see SimpleCommand
 * @see [CommandManager.executeCommand]
 */
+@ConsoleExperimentalApi("Not yet supported")
 public abstract class JSimpleCommand(
    owner: CommandOwner,
    @ResolveContext(COMMAND_NAME) primaryName: String,
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandCall.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandCall.kt
@ -0,0 +1,41 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:OptIn(ExperimentalStdlibApi::class)
+
+package net.mamoe.mirai.console.command.parse
+
+import net.mamoe.mirai.console.command.Command
+import net.mamoe.mirai.console.command.CommandSender
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+
+/**
+ * Unresolved [CommandCall].
+ */
+@ExperimentalCommandDescriptors
+public interface CommandCall {
+    public val caller: CommandSender
+
+    /**
+     * One of callee [Command]'s [Command.allNames]
+     */
+    public val calleeName: String
+
+    /**
+     * Explicit value arguments
+     */
+    public val valueArguments: List<CommandValueArgument>
+}
+
+@ExperimentalCommandDescriptors
+public class CommandCallImpl(
+    override val caller: CommandSender,
+    override val calleeName: String,
+    override val valueArguments: List<CommandValueArgument>,
+) : CommandCall
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandCallParser.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandCallParser.kt
@ -0,0 +1,46 @@
+package net.mamoe.mirai.console.command.parse
+
+import net.mamoe.mirai.console.command.CommandSender
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.resolve.CommandCallResolver
+import net.mamoe.mirai.console.command.resolve.ResolvedCommandCall
+import net.mamoe.mirai.console.extensions.CommandCallParserProvider
+import net.mamoe.mirai.console.internal.extension.GlobalComponentStorage
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.message.data.MessageChain
+
+/**
+ * Lexical and syntactical parser for transforming a [MessageChain] into [CommandCall]
+ *
+ * @see CommandCallResolver The call resolver for [CommandCall] to become [ResolvedCommandCall]
+ * @see CommandCallParserProvider The extension point
+ *
+ * @see SpaceSeparatedCommandCallParser
+ */
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public interface CommandCallParser {
+
+    /**
+     * Lexically and syntactically parse a [message] into [CommandCall], but performs nothing about resolving a call.
+     *
+     * @return `null` if unable to parse (i.e. due to syntax errors).
+     */
+    public fun parse(caller: CommandSender, message: MessageChain): CommandCall?
+
+    public companion object {
+        /**
+         * Calls [CommandCallParser]s provided by [CommandCallParserProvider] in [GlobalComponentStorage] sequentially,
+         * returning the first non-null result, `null` otherwise.
+         */
+        @JvmStatic
+        public fun MessageChain.parseCommandCall(sender: CommandSender): CommandCall? {
+            GlobalComponentStorage.run {
+                CommandCallParserProvider.useExtensions { provider ->
+                    provider.instance.parse(sender, this@parseCommandCall)?.let { return it }
+                }
+            }
+            return null
+        }
+    }
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandValueArgument.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/CommandValueArgument.kt
@ -0,0 +1,132 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:Suppress("unused")
+
+package net.mamoe.mirai.console.command.parse
+
+import net.mamoe.mirai.console.command.descriptor.*
+import net.mamoe.mirai.console.internal.data.castOrInternalError
+import net.mamoe.mirai.console.internal.data.classifierAsKClass
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.message.data.Message
+import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.message.data.MessageContent
+import net.mamoe.mirai.message.data.SingleMessage
+import kotlin.reflect.KType
+import kotlin.reflect.full.isSubtypeOf
+import kotlin.reflect.typeOf
+
+
+/**
+ * @see CommandValueArgument
+ */
+@ExperimentalCommandDescriptors
+public interface CommandArgument
+
+/**
+ * @see DefaultCommandValueArgument
+ */
+@ExperimentalCommandDescriptors
+public interface CommandValueArgument : CommandArgument {
+    public val type: KType
+
+    /**
+     * [MessageContent] if single argument
+     * [MessageChain] is vararg
+     */
+    public val value: Message
+    public val typeVariants: List<TypeVariant<*>>
+}
+
+/**
+ * The [CommandValueArgument] that doesn't vary in type (remaining [MessageContent]).
+ */
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public data class DefaultCommandValueArgument(
+    public override val value: Message,
+) : CommandValueArgument {
+    @OptIn(ExperimentalStdlibApi::class)
+    override val type: KType = typeOf<MessageContent>()
+    override val typeVariants: List<TypeVariant<*>> = listOf(
+        MessageContentTypeVariant,
+        MessageChainTypeVariant,
+        ContentStringTypeVariant,
+    )
+}
+
+@ExperimentalCommandDescriptors
+public fun <T> CommandValueArgument.mapValue(typeVariant: TypeVariant<T>): T = typeVariant.mapValue(this.value)
+
+
+@OptIn(ExperimentalStdlibApi::class)
+@ExperimentalCommandDescriptors
+public inline fun <reified T> CommandValueArgument.mapToType(): T =
+    mapToTypeOrNull() ?: throw  NoValueArgumentMappingException(this, typeOf<T>())
+
+@OptIn(ExperimentalStdlibApi::class)
+@ExperimentalCommandDescriptors
+public fun <T> CommandValueArgument.mapToType(type: KType): T =
+    mapToTypeOrNull(type) ?: throw  NoValueArgumentMappingException(this, type)
+
+@ExperimentalCommandDescriptors
+public fun <T> CommandValueArgument.mapToTypeOrNull(expectingType: KType): T? {
+    if (expectingType.isSubtypeOf(ARRAY_OUT_ANY_TYPE)) {
+        val arrayElementType = expectingType.arguments.single().type ?: ANY_TYPE
+
+        val result = ArrayList<Any?>()
+
+        when (val value = value) {
+            is MessageChain -> {
+                for (message in value) {
+                    result.add(mapToTypeOrNullImpl(arrayElementType, message))
+                }
+            }
+            else -> { // single
+                value.castOrInternalError<SingleMessage>()
+                result.add(mapToTypeOrNullImpl(arrayElementType, value))
+            }
+        }
+
+
+        @Suppress("UNCHECKED_CAST")
+        return result.toArray(arrayElementType.createArray(result.size)) as T
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    return mapToTypeOrNullImpl(expectingType, value) as T
+}
+
+private fun KType.createArray(size: Int): Array<Any?> {
+    return java.lang.reflect.Array.newInstance(this.classifierAsKClass().javaObjectType, size).castOrInternalError()
+}
+
+@OptIn(ExperimentalCommandDescriptors::class)
+private fun CommandValueArgument.mapToTypeOrNullImpl(expectingType: KType, value: Message): Any? {
+    @OptIn(ExperimentalStdlibApi::class)
+    val result = typeVariants
+        .filter { it.outType.isSubtypeOf(expectingType) }
+        .ifEmpty {
+            return null
+        }
+        .reduce { acc, typeVariant ->
+            if (acc.outType.isSubtypeOf(typeVariant.outType))
+                acc
+            else typeVariant
+        }
+    @Suppress("UNCHECKED_CAST")
+    return result.mapValue(value)
+}
+
+@ExperimentalCommandDescriptors
+public inline fun <reified T> CommandValueArgument.mapToTypeOrNull(): T? {
+    @OptIn(ExperimentalStdlibApi::class)
+    return mapToTypeOrNull(typeOf<T>())
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/SpaceSeparatedCommandCallParser.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/parse/SpaceSeparatedCommandCallParser.kt
@ -0,0 +1,26 @@
+package net.mamoe.mirai.console.command.parse
+
+import net.mamoe.mirai.console.command.CommandSender
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.extensions.CommandCallParserProvider
+import net.mamoe.mirai.console.internal.command.flattenCommandComponents
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.message.data.MessageContent
+import net.mamoe.mirai.message.data.content
+
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public object SpaceSeparatedCommandCallParser : CommandCallParser {
+    override fun parse(caller: CommandSender, message: MessageChain): CommandCall? {
+        val flatten = message.flattenCommandComponents().filterIsInstance<MessageContent>()
+        if (flatten.isEmpty()) return null
+        return CommandCallImpl(
+            caller = caller,
+            calleeName = flatten.first().content,
+            valueArguments = flatten.drop(1).map(::DefaultCommandValueArgument)
+        )
+    }
+
+    public object Provider : CommandCallParserProvider(SpaceSeparatedCommandCallParser)
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/BuiltInCommandCallResolver.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/BuiltInCommandCallResolver.kt
@ -0,0 +1,172 @@
+package net.mamoe.mirai.console.command.resolve
+
+import net.mamoe.mirai.console.command.Command
+import net.mamoe.mirai.console.command.CommandManager
+import net.mamoe.mirai.console.command.descriptor.*
+import net.mamoe.mirai.console.command.descriptor.ArgumentAcceptance.Companion.isNotAcceptable
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.command.parse.CommandValueArgument
+import net.mamoe.mirai.console.command.parse.DefaultCommandValueArgument
+import net.mamoe.mirai.console.extensions.CommandCallResolverProvider
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.console.util.safeCast
+import net.mamoe.mirai.message.data.EmptyMessageChain
+import net.mamoe.mirai.message.data.asMessageChain
+
+/**
+ * Builtin implementation of [CommandCallResolver]
+ */
+@ConsoleExperimentalApi
+@ExperimentalCommandDescriptors
+public object BuiltInCommandCallResolver : CommandCallResolver {
+    public object Provider : CommandCallResolverProvider(BuiltInCommandCallResolver)
+
+    override fun resolve(call: CommandCall): ResolvedCommandCall? {
+        val callee = CommandManager.matchCommand(call.calleeName) ?: return null
+
+        val valueArguments = call.valueArguments
+        val context = callee.safeCast<CommandArgumentContextAware>()?.context
+
+        val signature = resolveImpl(callee, valueArguments, context) ?: return null
+
+        return ResolvedCommandCallImpl(call.caller,
+            callee,
+            signature.variant,
+            signature.zippedArguments.map { it.second },
+            context ?: EmptyCommandArgumentContext)
+    }
+
+    private data class ResolveData(
+        val variant: CommandSignatureVariant,
+        val zippedArguments: List<Pair<AbstractCommandValueParameter<*>, CommandValueArgument>>,
+        val argumentAcceptances: List<ArgumentAcceptanceWithIndex>,
+        val remainingParameters: List<AbstractCommandValueParameter<*>>,
+    ) {
+        val remainingOptionalCount: Int = remainingParameters.count { it.isOptional }
+    }
+
+    private data class ArgumentAcceptanceWithIndex(
+        val index: Int,
+        val acceptance: ArgumentAcceptance,
+    )
+
+    private fun resolveImpl(
+        callee: Command,
+        valueArguments: List<CommandValueArgument>,
+        context: CommandArgumentContext?,
+    ): ResolveData? {
+
+
+        callee.overloads
+            .mapNotNull l@{ signature ->
+                val valueParameters = signature.valueParameters
+
+                val zipped = valueParameters.zip(valueArguments).toMutableList()
+
+                val remainingParameters = valueParameters.drop(zipped.size).toMutableList()
+
+                if (remainingParameters.any { !it.isOptional && !it.isVararg }) return@l null // not enough args. // vararg can be empty.
+
+                if (zipped.isEmpty()) {
+                    ResolveData(
+                        variant = signature,
+                        zippedArguments = emptyList(),
+                        argumentAcceptances = emptyList(),
+                        remainingParameters = remainingParameters,
+                    )
+                } else {
+                    if (valueArguments.size > valueParameters.size && zipped.last().first.isVararg) {
+                        // merge vararg arguments
+                        val (varargParameter, varargFirstArgument)
+                            = zipped.removeLast()
+
+                        zipped.add(varargParameter to DefaultCommandValueArgument(valueArguments.drop(zipped.size).map { it.value }.asMessageChain()))
+                    } else {
+                        // add default empty vararg argument
+                        val remainingVararg = remainingParameters.find { it.isVararg }
+                        if (remainingVararg != null) {
+                            zipped.add(remainingVararg to DefaultCommandValueArgument(EmptyMessageChain))
+                            remainingParameters.remove(remainingVararg)
+                        }
+                    }
+
+                    ResolveData(
+                        variant = signature,
+                        zippedArguments = zipped,
+                        argumentAcceptances = zipped.mapIndexed { index, (parameter, argument) ->
+                            val accepting = parameter.accepting(argument, context)
+                            if (accepting.isNotAcceptable) {
+                                return@l null // argument type not assignable
+                            }
+                            ArgumentAcceptanceWithIndex(index, accepting)
+                        },
+                        remainingParameters = remainingParameters
+                    )
+                }
+            }
+            .also { result -> result.singleOrNull()?.let { return it } }
+            .takeLongestMatches()
+            .ifEmpty { return null }
+            .also { result -> result.singleOrNull()?.let { return it } }
+            // take single ArgumentAcceptance.Direct
+            .also { list ->
+
+                val candidates = list
+                    .flatMap { phase ->
+                        phase.argumentAcceptances.filter { it.acceptance is ArgumentAcceptance.Direct }.map { phase to it }
+                    }
+                candidates.singleOrNull()?.let { return it.first } // single Direct
+                if (candidates.distinctBy { it.second.index }.size != candidates.size) {
+                    // Resolution ambiguity
+                    /*
+                    open class A
+                    open class AA: A()
+
+                    open class C
+                    open class CC: C()
+
+                    fun foo(a: A, c: CC) = 1
+                    fun foo(a: AA, c: C) = 1
+                     */
+                    // The call is foo(AA(), C()) or foo(A(), CC())
+                    return null
+                }
+            }
+
+        return null
+    }
+
+    /*
+
+
+open class A
+open class B : A()
+open class C : A()
+open class D : C()
+open class BB : B()
+
+fun foo(a: A, c: C) = 1
+//fun foo(a: A, c: A) = 1
+//fun foo(a: A, c: C, def: Int = 0) = 1
+fun foo(a: B, c: C, d: D) = ""
+
+fun foo(b: BB, a: A, d: C) = 1.0
+
+
+fun main() {
+    val a = foo(D(), D()) // int
+    val b = foo(A(), C()) // int
+    val d = foo(BB(), c = C(), D()) // string
+}
+     */
+
+    private fun List<ResolveData>.takeLongestMatches(): Collection<ResolveData> {
+        if (isEmpty()) return emptyList()
+        return associateWith {
+            it.variant.valueParameters.size - it.remainingOptionalCount * 1.001 // slightly lower priority with optional defaults.
+        }.let { m ->
+            val maxMatch = m.values.maxByOrNull { it }
+            m.filter { it.value == maxMatch }.keys
+        }
+    }
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/CommandCallResolver.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/CommandCallResolver.kt
@ -0,0 +1,41 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.command.resolve
+
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.extensions.CommandCallResolverProvider
+import net.mamoe.mirai.console.internal.extension.GlobalComponentStorage
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+
+/**
+ * The resolver converting a [CommandCall] into [ResolvedCommandCall] based on registered []
+ *
+ * @see CommandCallResolverProvider The provider to instances of this class
+ * @see BuiltInCommandCallResolver The builtin implementation
+ */
+@ExperimentalCommandDescriptors
+public interface CommandCallResolver {
+    public fun resolve(call: CommandCall): ResolvedCommandCall?
+
+    public companion object {
+        @JvmName("resolveCall")
+        @ConsoleExperimentalApi
+        @ExperimentalCommandDescriptors
+        public fun CommandCall.resolve(): ResolvedCommandCall? {
+            GlobalComponentStorage.run {
+                CommandCallResolverProvider.useExtensions { provider ->
+                    provider.instance.resolve(this@resolve)?.let { return it }
+                }
+            }
+            return null
+        }
+    }
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/ResolvedCommandCall.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/resolve/ResolvedCommandCall.kt
@ -0,0 +1,87 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.command.resolve
+
+import net.mamoe.mirai.console.command.Command
+import net.mamoe.mirai.console.command.CommandSender
+import net.mamoe.mirai.console.command.CompositeCommand
+import net.mamoe.mirai.console.command.descriptor.*
+import net.mamoe.mirai.console.command.parse.CommandCall
+import net.mamoe.mirai.console.command.parse.CommandValueArgument
+import net.mamoe.mirai.console.command.parse.mapToTypeOrNull
+import net.mamoe.mirai.console.internal.data.classifierAsKClass
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.console.util.cast
+import kotlin.LazyThreadSafetyMode.PUBLICATION
+
+/**
+ * The resolved [CommandCall].
+ *
+ * @see ResolvedCommandCallImpl
+ */
+@ExperimentalCommandDescriptors
+public interface ResolvedCommandCall {
+    public val caller: CommandSender
+
+    /**
+     * The callee [Command]
+     */
+    public val callee: Command
+
+    /**
+     * The callee [CommandSignatureVariant], specifically a sub command from [CompositeCommand]
+     */
+    public val calleeSignature: CommandSignatureVariant
+
+    /**
+     * Original arguments
+     */
+    public val rawValueArguments: List<CommandValueArgument>
+
+    /**
+     * Resolved value arguments arranged mapping the [CommandSignatureVariant.valueParameters] by index.
+     *
+     * **Implementation details**: Lazy calculation.
+     */
+    @ConsoleExperimentalApi
+    public val resolvedValueArguments: List<ResolvedCommandValueArgument<*>>
+
+    public companion object
+}
+
+@ExperimentalCommandDescriptors
+public data class ResolvedCommandValueArgument<T>(
+    val parameter: CommandValueParameter<T>,
+    val value: T,
+)
+
+// Don't move into companion, compilation error
+@ExperimentalCommandDescriptors
+public suspend inline fun ResolvedCommandCall.call() {
+    return this@call.calleeSignature.call(this@call)
+}
+
+@ExperimentalCommandDescriptors
+public class ResolvedCommandCallImpl(
+    override val caller: CommandSender,
+    override val callee: Command,
+    override val calleeSignature: CommandSignatureVariant,
+    override val rawValueArguments: List<CommandValueArgument>,
+    private val context: CommandArgumentContext,
+) : ResolvedCommandCall {
+    override val resolvedValueArguments: List<ResolvedCommandValueArgument<*>> by lazy(PUBLICATION) {
+        calleeSignature.valueParameters.zip(rawValueArguments).map { (parameter, argument) ->
+            val value = argument.mapToTypeOrNull(parameter.type) ?: context[parameter.type.classifierAsKClass()]?.parse(argument.value, caller)
+            ?: throw  NoValueArgumentMappingException(argument, parameter.type)
+            // TODO: 2020/10/17 consider vararg and optional
+            ResolvedCommandValueArgument(parameter.cast(), value)
+        }
+    }
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/data/AutoSavePluginData.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/data/AutoSavePluginData.kt
@ -14,7 +14,7 @@ package net.mamoe.mirai.console.data
 import kotlinx.atomicfu.atomic
 import kotlinx.coroutines.*
 import net.mamoe.mirai.console.MiraiConsole
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
+import net.mamoe.mirai.console.internal.data.qualifiedNameOrTip
 import net.mamoe.mirai.console.internal.plugin.updateWhen
 import net.mamoe.mirai.console.util.ConsoleExperimentalApi
 import net.mamoe.mirai.utils.*
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extension/ExtensionPoint.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extension/ExtensionPoint.kt
@ -24,6 +24,12 @@ public open class AbstractExtensionPoint<T : Extension>(
    public override val extensionType: KClass<T>,
 ) : ExtensionPoint<T>

+public open class InstanceExtensionPoint<E : InstanceExtension<T>, T>(
+    extensionType: KClass<E>,
+    public vararg val builtinImplementations: E,
+) : AbstractExtensionPoint<E>(extensionType)
+
+
 /**
 * 表示一个 [SingletonExtension] 的 [ExtensionPoint]
 */
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/CommandCallParserProvider.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/CommandCallParserProvider.kt
@ -0,0 +1,25 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.extensions
+
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.parse.CommandCallParser
+import net.mamoe.mirai.console.command.parse.SpaceSeparatedCommandCallParser
+import net.mamoe.mirai.console.extension.InstanceExtension
+import net.mamoe.mirai.console.extension.InstanceExtensionPoint
+
+/**
+ * The provider of [CommandCallParser]
+ */
+@ExperimentalCommandDescriptors
+public open class CommandCallParserProvider(override val instance: CommandCallParser) : InstanceExtension<CommandCallParser> {
+    public companion object ExtensionPoint :
+        InstanceExtensionPoint<CommandCallParserProvider, CommandCallParser>(CommandCallParserProvider::class, SpaceSeparatedCommandCallParser.Provider)
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/CommandCallResolverProvider.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/CommandCallResolverProvider.kt
@ -0,0 +1,22 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.extensions
+
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.resolve.BuiltInCommandCallResolver
+import net.mamoe.mirai.console.command.resolve.CommandCallResolver
+import net.mamoe.mirai.console.extension.InstanceExtension
+import net.mamoe.mirai.console.extension.InstanceExtensionPoint
+
+@ExperimentalCommandDescriptors
+public open class CommandCallResolverProvider(override val instance: CommandCallResolver) : InstanceExtension<CommandCallResolver> {
+    public companion object ExtensionPoint :
+        InstanceExtensionPoint<CommandCallResolverProvider, CommandCallResolver>(CommandCallResolverProvider::class, BuiltInCommandCallResolver.Provider)
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/SingletonExtensionSelector.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/extensions/SingletonExtensionSelector.kt
@ -29,7 +29,7 @@ import kotlin.reflect.KClass
 */
 public interface SingletonExtensionSelector : FunctionExtension {
    public data class Registry<T : Extension>(
-        val plugin: Plugin,
+        val plugin: Plugin?,
        val extension: T,
    )

@ -55,11 +55,11 @@ public interface SingletonExtensionSelector : FunctionExtension {
                instances.isEmpty() -> BuiltInSingletonExtensionSelector
                instances.size == 1 -> {
                    instances.single().also { (plugin, ext) ->
-                        MiraiConsole.mainLogger.info { "Loaded SingletonExtensionSelector: $ext from ${plugin.name}" }
+                        MiraiConsole.mainLogger.info { "Loaded SingletonExtensionSelector: $ext from ${plugin?.name ?: "<builtin>"}" }
                    }.extension
                }
                else -> {
-                    error("Found too many SingletonExtensionSelectors: ${instances.joinToString { (p, i) -> "'$i' from '${p.name}'" }}. Check your plugins and ensure there is only one external SingletonExtensionSelectors")
+                    error("Found too many SingletonExtensionSelectors: ${instances.joinToString { (p, i) -> "'$i' from '${p?.name ?: "<builtin>"}'" }}. Check your plugins and ensure there is only one external SingletonExtensionSelectors")
                }
            }
        }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CommandManagerImpl.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CommandManagerImpl.kt
@ -15,18 +15,25 @@ import kotlinx.coroutines.CoroutineScope
 import net.mamoe.mirai.console.MiraiConsole
 import net.mamoe.mirai.console.command.*
 import net.mamoe.mirai.console.command.Command.Companion.allNames
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.findDuplicate
 import net.mamoe.mirai.console.command.CommandSender.Companion.toCommandSender
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.parse.CommandCallParser.Companion.parseCommandCall
+import net.mamoe.mirai.console.command.resolve.CommandCallResolver.Companion.resolve
+import net.mamoe.mirai.console.permission.PermissionService.Companion.testPermission
+import net.mamoe.mirai.console.util.CoroutineScopeUtils.childScope
 import net.mamoe.mirai.event.Listener
 import net.mamoe.mirai.event.subscribeAlways
 import net.mamoe.mirai.message.MessageEvent
+import net.mamoe.mirai.message.data.EmptyMessageChain
 import net.mamoe.mirai.message.data.Message
-import net.mamoe.mirai.message.data.MessageContent
 import net.mamoe.mirai.message.data.asMessageChain
 import net.mamoe.mirai.message.data.content
 import net.mamoe.mirai.utils.MiraiLogger
 import java.util.concurrent.locks.ReentrantLock

-internal object CommandManagerImpl : CommandManager, CoroutineScope by CoroutineScope(MiraiConsole.job) {
+@OptIn(ExperimentalCommandDescriptors::class)
+internal object CommandManagerImpl : CommandManager, CoroutineScope by MiraiConsole.childScope("CommandManagerImpl") {
    private val logger: MiraiLogger by lazy {
        MiraiConsole.createLogger("command")
    }
@ -48,11 +55,11 @@ internal object CommandManagerImpl : CommandManager, CoroutineScope by Coroutine
    /**
     * 从原始的 command 中解析出 Command 对象
     */
-    internal fun matchCommand(rawCommand: String): Command? {
-        if (rawCommand.startsWith(commandPrefix)) {
-            return requiredPrefixCommandMap[rawCommand.substringAfter(commandPrefix).toLowerCase()]
+    override fun matchCommand(commandName: String): Command? {
+        if (commandName.startsWith(commandPrefix)) {
+            return requiredPrefixCommandMap[commandName.substringAfter(commandPrefix).toLowerCase()]
        }
-        return optionalPrefixCommandMap[rawCommand.toLowerCase()]
+        return optionalPrefixCommandMap[commandName.toLowerCase()]
    }

    internal val commandListener: Listener<MessageEvent> by lazy {
@ -65,13 +72,17 @@ internal object CommandManagerImpl : CommandManager, CoroutineScope by Coroutine
        ) {
            val sender = this.toCommandSender()

-            when (val result = sender.executeCommand(message)) {
+            when (val result = executeCommand(sender, message)) {
                is CommandExecuteResult.PermissionDenied -> {
                    if (!result.command.prefixOptional || message.content.startsWith(CommandManager.commandPrefix)) {
                        sender.sendMessage("权限不足")
                        intercept()
                    }
                }
+                is CommandExecuteResult.IllegalArgument -> {
+                    result.exception.message?.let { sender.sendMessage(it) }
+                    intercept()
+                }
                is CommandExecuteResult.Success -> {
                    intercept()
                }
@ -79,7 +90,7 @@ internal object CommandManagerImpl : CommandManager, CoroutineScope by Coroutine
                    sender.catchExecutionException(result.exception)
                    intercept()
                }
-                is CommandExecuteResult.CommandNotFound -> {
+                is CommandExecuteResult.UnresolvedCall -> {
                    // noop
                }
            }
@ -90,102 +101,90 @@ internal object CommandManagerImpl : CommandManager, CoroutineScope by Coroutine
    ///// IMPL


-    override val CommandOwner.registeredCommands: List<Command> get() = _registeredCommands.filter { it.owner == this }
+    override fun getRegisteredCommands(owner: CommandOwner): List<Command> = _registeredCommands.filter { it.owner == owner }
    override val allRegisteredCommands: List<Command> get() = _registeredCommands.toList() // copy
    override val commandPrefix: String get() = "/"
-    override fun CommandOwner.unregisterAllCommands() {
-        for (registeredCommand in registeredCommands) {
-            registeredCommand.unregister()
+    override fun unregisterAllCommands(owner: CommandOwner) {
+        for (registeredCommand in getRegisteredCommands(owner)) {
+            unregisterCommand(registeredCommand)
        }
    }

-    override fun Command.register(override: Boolean): Boolean {
-        if (this is CompositeCommand) this.subCommands // init lazy
+    override fun registerCommand(command: Command, override: Boolean): Boolean {
+        if (command is CompositeCommand) {
+            command.overloads  // init lazy
+        }
        kotlin.runCatching {
-            this.permission // init lazy
-            this.secondaryNames // init lazy
-            this.description // init lazy
-            this.usage // init lazy
+            command.permission // init lazy
+            command.secondaryNames // init lazy
+            command.description // init lazy
+            command.usage // init lazy
        }.onFailure {
-            throw IllegalStateException("Failed to init command ${this@register}.", it)
+            throw IllegalStateException("Failed to init command ${command}.", it)
        }

-        modifyLock.withLock {
+        this@CommandManagerImpl.modifyLock.withLock {
            if (!override) {
-                if (findDuplicate() != null) return false
+                if (command.findDuplicate() != null) return false
            }
-            _registeredCommands.add(this@register)
-            if (this.prefixOptional) {
-                for (name in this.allNames) {
+            this@CommandManagerImpl._registeredCommands.add(command)
+            if (command.prefixOptional) {
+                for (name in command.allNames) {
                    val lowerCaseName = name.toLowerCase()
-                    optionalPrefixCommandMap[lowerCaseName] = this
-                    requiredPrefixCommandMap[lowerCaseName] = this
+                    this@CommandManagerImpl.optionalPrefixCommandMap[lowerCaseName] = command
+                    this@CommandManagerImpl.requiredPrefixCommandMap[lowerCaseName] = command
                }
            } else {
-                for (name in this.allNames) {
+                for (name in command.allNames) {
                    val lowerCaseName = name.toLowerCase()
-                    optionalPrefixCommandMap.remove(lowerCaseName) // ensure resolution consistency
-                    requiredPrefixCommandMap[lowerCaseName] = this
+                    this@CommandManagerImpl.optionalPrefixCommandMap.remove(lowerCaseName) // ensure resolution consistency
+                    this@CommandManagerImpl.requiredPrefixCommandMap[lowerCaseName] = command
                }
            }
            return true
        }
    }

-    override fun Command.findDuplicate(): Command? =
-        _registeredCommands.firstOrNull { it.allNames intersectsIgnoringCase this.allNames }
+    override fun findDuplicateCommand(command: Command): Command? =
+        _registeredCommands.firstOrNull { it.allNames intersectsIgnoringCase command.allNames }

-    override fun Command.unregister(): Boolean = modifyLock.withLock {
-        if (this.prefixOptional) {
-            this.allNames.forEach {
-                optionalPrefixCommandMap.remove(it)
+    override fun unregisterCommand(command: Command): Boolean = modifyLock.withLock {
+        if (command.prefixOptional) {
+            command.allNames.forEach {
+                optionalPrefixCommandMap.remove(it.toLowerCase())
            }
        }
-        this.allNames.forEach {
-            requiredPrefixCommandMap.remove(it)
+        command.allNames.forEach {
+            requiredPrefixCommandMap.remove(it.toLowerCase())
        }
-        _registeredCommands.remove(this)
+        _registeredCommands.remove(command)
    }

-    override fun Command.isRegistered(): Boolean = this in _registeredCommands
-
-    override suspend fun Command.execute(
-        sender: CommandSender,
-        arguments: Message,
-        checkPermission: Boolean
-    ): CommandExecuteResult {
-        return sender.executeCommandInternal(
-            this,
-            arguments.flattenCommandComponents(),
-            primaryName,
-            checkPermission
-        )
+    override fun isCommandRegistered(command: Command): Boolean = command in _registeredCommands
 }

-    override suspend fun Command.execute(
-        sender: CommandSender,
-        arguments: String,
-        checkPermission: Boolean
-    ): CommandExecuteResult {
-        return sender.executeCommandInternal(
-            this,
-            arguments.flattenCommandComponents(),
-            primaryName,
-            checkPermission
-        )
-    }

-    override suspend fun CommandSender.executeCommand(
+// Don't move into CommandManager, compilation error / VerifyError
+@OptIn(ExperimentalCommandDescriptors::class)
+internal suspend fun executeCommandImpl(
    message: Message,
-        checkPermission: Boolean
+    caller: CommandSender,
+    checkPermission: Boolean,
 ): CommandExecuteResult {
-        val msg = message.asMessageChain().filterIsInstance<MessageContent>()
-        if (msg.isEmpty()) return CommandExecuteResult.CommandNotFound("")
-        return executeCommandInternal(msg, msg[0].content.substringBefore(' '), checkPermission)
+    val call = message.asMessageChain().parseCommandCall(caller) ?: return CommandExecuteResult.UnresolvedCall("")
+    val resolved = call.resolve() ?: return CommandExecuteResult.UnresolvedCall(call.calleeName)
+
+    val command = resolved.callee
+
+    if (checkPermission && !command.permission.testPermission(caller)) {
+        return CommandExecuteResult.PermissionDenied(command, call.calleeName)
    }

-    override suspend fun CommandSender.executeCommand(message: String, checkPermission: Boolean): CommandExecuteResult {
-        if (message.isBlank()) return CommandExecuteResult.CommandNotFound("")
-        return executeCommandInternal(message, message.substringBefore(' '), checkPermission)
+    return try {
+        resolved.calleeSignature.call(resolved)
+        CommandExecuteResult.Success(resolved.callee, call.calleeName, EmptyMessageChain)
+    } catch (e: Throwable) {
+        CommandExecuteResult.ExecutionFailed(e, resolved.callee, call.calleeName, EmptyMessageChain)
    }
 }
+
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CommandReflector.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CommandReflector.kt
@ -0,0 +1,242 @@
+package net.mamoe.mirai.console.internal.command
+
+import net.mamoe.mirai.console.command.*
+import net.mamoe.mirai.console.command.descriptor.*
+import net.mamoe.mirai.console.internal.data.classifierAsKClass
+import net.mamoe.mirai.console.internal.data.classifierAsKClassOrNull
+import net.mamoe.mirai.console.util.ConsoleExperimentalApi
+import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.message.data.PlainText
+import net.mamoe.mirai.message.data.SingleMessage
+import net.mamoe.mirai.message.data.buildMessageChain
+import kotlin.reflect.KFunction
+import kotlin.reflect.KParameter
+import kotlin.reflect.KVisibility
+import kotlin.reflect.full.*
+
+
+internal val ILLEGAL_SUB_NAME_CHARS = "\\/!@#$%^&*()_+-={}[];':\",.<>?`~".toCharArray()
+
+internal fun Any.flattenCommandComponents(): MessageChain = buildMessageChain {
+    when (this@flattenCommandComponents) {
+        is PlainText -> this@flattenCommandComponents.content.splitToSequence(' ').filterNot { it.isBlank() }
+            .forEach { +PlainText(it) }
+        is CharSequence -> this@flattenCommandComponents.splitToSequence(' ').filterNot { it.isBlank() }
+            .forEach { +PlainText(it) }
+        is SingleMessage -> add(this@flattenCommandComponents)
+        is Array<*> -> this@flattenCommandComponents.forEach { if (it != null) addAll(it.flattenCommandComponents()) }
+        is Iterable<*> -> this@flattenCommandComponents.forEach { if (it != null) addAll(it.flattenCommandComponents()) }
+        else -> add(this@flattenCommandComponents.toString())
+    }
+}
+
+@Suppress("INVISIBLE_REFERENCE", "INVISIBLE_MEMBER")
+internal object CompositeCommandSubCommandAnnotationResolver :
+    SubCommandAnnotationResolver {
+    override fun hasAnnotation(ownerCommand: Command, function: KFunction<*>) =
+        function.hasAnnotation<CompositeCommand.SubCommand>()
+
+    override fun getSubCommandNames(ownerCommand: Command, function: KFunction<*>): Array<out String> {
+        val annotated = function.findAnnotation<CompositeCommand.SubCommand>()!!.value
+        return if (annotated.isEmpty()) arrayOf(function.name)
+        else annotated
+    }
+
+    override fun getAnnotatedName(ownerCommand: Command, parameter: KParameter): String? =
+        parameter.findAnnotation<CompositeCommand.Name>()?.value
+
+    override fun getDescription(ownerCommand: Command, function: KFunction<*>): String? =
+        function.findAnnotation<CompositeCommand.Description>()?.value
+}
+
+@Suppress("INVISIBLE_REFERENCE", "INVISIBLE_MEMBER")
+internal object SimpleCommandSubCommandAnnotationResolver :
+    SubCommandAnnotationResolver {
+    override fun hasAnnotation(ownerCommand: Command, function: KFunction<*>) =
+        function.hasAnnotation<SimpleCommand.Handler>()
+
+    override fun getSubCommandNames(ownerCommand: Command, function: KFunction<*>): Array<out String> =
+        ownerCommand.secondaryNames
+
+    override fun getAnnotatedName(ownerCommand: Command, parameter: KParameter): String? =
+        parameter.findAnnotation<SimpleCommand.Name>()?.value
+
+    override fun getDescription(ownerCommand: Command, function: KFunction<*>): String? =
+        ownerCommand.description
+}
+
+internal interface SubCommandAnnotationResolver {
+    fun hasAnnotation(ownerCommand: Command, function: KFunction<*>): Boolean
+    fun getSubCommandNames(ownerCommand: Command, function: KFunction<*>): Array<out String>
+    fun getAnnotatedName(ownerCommand: Command, parameter: KParameter): String?
+    fun getDescription(ownerCommand: Command, function: KFunction<*>): String?
+}
+
+@ConsoleExperimentalApi
+public class IllegalCommandDeclarationException : Exception {
+    public override val message: String?
+
+    public constructor(
+        ownerCommand: Command,
+        correspondingFunction: KFunction<*>,
+        message: String?,
+    ) : super("Illegal command declaration: ${correspondingFunction.name} declared in ${ownerCommand::class.qualifiedName}") {
+        this.message = message
+    }
+
+    public constructor(
+        ownerCommand: Command,
+        message: String?,
+    ) : super("Illegal command declaration: ${ownerCommand::class.qualifiedName}") {
+        this.message = message
+    }
+}
+
+@OptIn(ExperimentalCommandDescriptors::class)
+internal class CommandReflector(
+    val command: Command,
+    val annotationResolver: SubCommandAnnotationResolver,
+) {
+
+    @Suppress("NOTHING_TO_INLINE")
+    private inline fun KFunction<*>.illegalDeclaration(
+        message: String,
+    ): Nothing {
+        throw IllegalCommandDeclarationException(command, this, message)
+    }
+
+    private fun KFunction<*>.isSubCommandFunction(): Boolean = annotationResolver.hasAnnotation(command, this)
+    private fun KFunction<*>.checkExtensionReceiver() {
+        this.extensionReceiverParameter?.let { receiver ->
+            if (receiver.type.classifierAsKClassOrNull()?.isSubclassOf(CommandSender::class) != true) {
+                illegalDeclaration("Extension receiver parameter type is not subclass of CommandSender.")
+            }
+        }
+    }
+
+    private fun KFunction<*>.checkNames() {
+        val names = annotationResolver.getSubCommandNames(command, this)
+        for (name in names) {
+            ILLEGAL_SUB_NAME_CHARS.find { it in name }?.let {
+                illegalDeclaration("'$it' is forbidden in command name.")
+            }
+        }
+    }
+
+    private fun KFunction<*>.checkModifiers() {
+        if (isInline) illegalDeclaration("Command function cannot be inline")
+        if (visibility == KVisibility.PRIVATE) illegalDeclaration("Command function must be accessible from Mirai Console, that is, effectively public.")
+        if (this.hasAnnotation<JvmStatic>()) illegalDeclaration("Command function must not be static.")
+
+        // should we allow abstract?
+
+        // if (isAbstract) illegalDeclaration("Command function cannot be abstract")
+    }
+
+    fun generateUsage(overloads: Iterable<CommandSignatureVariantFromKFunction>): String {
+        return overloads.joinToString("\n") { subcommand ->
+            buildString {
+                if (command.prefixOptional) {
+                    append("(")
+                    append(CommandManager.commandPrefix)
+                    append(")")
+                } else {
+                    append(CommandManager.commandPrefix)
+                }
+                if (command is CompositeCommand) {
+                    append(command.primaryName)
+                    append(" ")
+                }
+                append(subcommand.valueParameters.joinToString(" ") { it.render() })
+                annotationResolver.getDescription(command, subcommand.originFunction).let { description ->
+                    append("   ")
+                    append(description)
+                }
+            }
+        }
+    }
+
+
+    companion object {
+
+        private fun <T> AbstractCommandValueParameter<T>.render(): String {
+            return when (this) {
+                is AbstractCommandValueParameter.Extended,
+                is AbstractCommandValueParameter.UserDefinedType<*>,
+                -> {
+                    "<${this.name ?: this.type.classifierAsKClass().simpleName}>"
+                }
+                is AbstractCommandValueParameter.StringConstant -> {
+                    this.expectingValue
+                }
+            }
+        }
+    }
+
+    fun validate(variants: List<CommandSignatureVariantFromKFunctionImpl>) {
+
+        data class ErasedParameters(
+            val name: String,
+            val x: String,
+        )
+        variants
+    }
+
+    @Throws(IllegalCommandDeclarationException::class)
+    fun findSubCommands(): List<CommandSignatureVariantFromKFunctionImpl> {
+        return command::class.functions // exclude static later
+            .asSequence()
+            .filter { it.isSubCommandFunction() }
+            .onEach { it.checkExtensionReceiver() }
+            .onEach { it.checkModifiers() }
+            .onEach { it.checkNames() }
+            .map { function ->
+
+                val functionNameAsValueParameter =
+                    annotationResolver.getSubCommandNames(command, function).mapIndexed { index, s -> createStringConstantParameter(index, s) }
+
+                val functionValueParameters =
+                    function.valueParameters.associateBy { it.toUserDefinedCommandParameter() }
+
+                CommandSignatureVariantFromKFunctionImpl(
+                    receiverParameter = function.extensionReceiverParameter?.toCommandReceiverParameter(),
+                    valueParameters = functionNameAsValueParameter + functionValueParameters.keys,
+                    originFunction = function
+                ) { call ->
+                    val args = LinkedHashMap<KParameter, Any?>()
+
+                    for ((commandParameter, value) in call.resolvedValueArguments) {
+                        if (commandParameter is AbstractCommandValueParameter.StringConstant) {
+                            continue
+                        }
+                        val functionParameter =
+                            functionValueParameters[commandParameter] ?: error("Could not find a corresponding function parameter '${commandParameter.name}'")
+                        args[functionParameter] = value
+                    }
+
+                    val instanceParameter = function.instanceParameter
+                    if (instanceParameter != null) {
+                        args[instanceParameter] = command
+                    }
+                    function.callSuspendBy(args)
+                }
+            }.toList()
+    }
+
+    private fun KParameter.toCommandReceiverParameter(): CommandReceiverParameter<out CommandSender>? {
+        check(!this.isVararg) { "Receiver cannot be vararg." }
+        check(this.type.classifierAsKClass().isSubclassOf(CommandSender::class)) { "Receiver must be subclass of CommandSender" }
+
+        return CommandReceiverParameter(this.type.isMarkedNullable, this.type)
+    }
+
+    private fun createStringConstantParameter(index: Int, expectingValue: String): AbstractCommandValueParameter.StringConstant {
+        return AbstractCommandValueParameter.StringConstant("#$index", expectingValue)
+    }
+
+    private fun KParameter.toUserDefinedCommandParameter(): AbstractCommandValueParameter.UserDefinedType<*> {
+        return AbstractCommandValueParameter.UserDefinedType<Any?>(nameForCommandParameter(), this.isOptional, this.isVararg, this.type) // Any? is erased
+    }
+
+    private fun KParameter.nameForCommandParameter(): String? = annotationResolver.getAnnotatedName(command, this) ?: this.name
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CompositeCommand.CommandParam.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CompositeCommand.CommandParam.kt
@ -12,22 +12,24 @@
 package net.mamoe.mirai.console.internal.command

 import net.mamoe.mirai.console.command.CompositeCommand
-import net.mamoe.mirai.console.command.description.CommandArgumentParser
-import java.lang.reflect.Parameter
-import kotlin.reflect.KClass
+import net.mamoe.mirai.console.command.descriptor.CommandValueArgumentParser
+import kotlin.reflect.KParameter
+import kotlin.reflect.KType

+/*
 internal fun Parameter.toCommandParam(): CommandParameter<*> {
    val name = getAnnotation(CompositeCommand.Name::class.java)
    return CommandParameter(
        name?.value ?: this.name
        ?: throw IllegalArgumentException("Cannot construct CommandParam from a unnamed param"),
-        this.type.kotlin
+        this.type.kotlin,
+        null
    )
 }
+*/

 /**
 * 指令形式参数.
- * @see toCommandParam
 */
 internal data class CommandParameter<T : Any>(
    /**
@ -35,24 +37,27 @@ internal data class CommandParameter<T : Any>(
     */
    val name: String,
    /**
-     * 参数类型. 将从 [CompositeCommand.context] 中寻找 [CommandArgumentParser] 解析.
+     * 参数类型. 将从 [CompositeCommand.context] 中寻找 [CommandValueArgumentParser] 解析.
     */
-    val type: KClass<T> // exact type
+    val type: KType, // exact type
+    val parameter: KParameter, // source parameter
+) {
+    constructor(name: String, type: KType, parameter: KParameter, parser: CommandValueArgumentParser<T>) : this(
+        name, type, parameter
    ) {
-    constructor(name: String, type: KClass<T>, parser: CommandArgumentParser<T>) : this(name, type) {
        this._overrideParser = parser
    }

    @Suppress("PropertyName")
    @JvmField
-    internal var _overrideParser: CommandArgumentParser<T>? = null
+    internal var _overrideParser: CommandValueArgumentParser<T>? = null


    /**
-     * 覆盖的 [CommandArgumentParser].
+     * 覆盖的 [CommandValueArgumentParser].
     *
-     * 如果非 `null`, 将不会从 [CommandArgumentContext] 寻找 [CommandArgumentParser]
+     * 如果非 `null`, 将不会从 [CommandArgumentContext] 寻找 [CommandValueArgumentParser]
     */
-    val overrideParser: CommandArgumentParser<T>? get() = _overrideParser
+    val overrideParser: CommandValueArgumentParser<T>? get() = _overrideParser
 }

--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CompositeCommandInternal.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/CompositeCommandInternal.kt
@ -1,349 +0,0 @@
-/*
- * Copyright 2019-2020 Mamoe Technologies and contributors.
- *
- * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- * Use of this source code is governed by the GNU AFFERO GENERAL PUBLIC LICENSE version 3 license that can be found via the following link.
- *
- * https://github.com/mamoe/mirai/blob/master/LICENSE
- */
-
-@file:Suppress("NOTHING_TO_INLINE", "MemberVisibilityCanBePrivate", "INVISIBLE_REFERENCE", "INVISIBLE_MEMBER")
-
-package net.mamoe.mirai.console.internal.command
-
-import net.mamoe.mirai.console.command.*
-import net.mamoe.mirai.console.command.description.CommandArgumentContext
-import net.mamoe.mirai.console.command.description.CommandArgumentContextAware
-import net.mamoe.mirai.console.internal.data.kClassQualifiedNameOrTip
-import net.mamoe.mirai.console.permission.Permission
-import net.mamoe.mirai.console.permission.PermissionService.Companion.testPermission
-import net.mamoe.mirai.message.data.*
-import kotlin.reflect.KAnnotatedElement
-import kotlin.reflect.KClass
-import kotlin.reflect.KFunction
-import kotlin.reflect.full.callSuspend
-import kotlin.reflect.full.declaredFunctions
-import kotlin.reflect.full.findAnnotation
-import kotlin.reflect.full.isSubclassOf
-
-internal object CompositeCommandSubCommandAnnotationResolver :
-    AbstractReflectionCommand.SubCommandAnnotationResolver {
-    override fun hasAnnotation(baseCommand: AbstractReflectionCommand, function: KFunction<*>) =
-        function.hasAnnotation<CompositeCommand.SubCommand>()
-
-    override fun getSubCommandNames(baseCommand: AbstractReflectionCommand, function: KFunction<*>): Array<out String> =
-        function.findAnnotation<CompositeCommand.SubCommand>()!!.value
-}
-
-internal object SimpleCommandSubCommandAnnotationResolver :
-    AbstractReflectionCommand.SubCommandAnnotationResolver {
-    override fun hasAnnotation(baseCommand: AbstractReflectionCommand, function: KFunction<*>) =
-        function.hasAnnotation<SimpleCommand.Handler>()
-
-    override fun getSubCommandNames(baseCommand: AbstractReflectionCommand, function: KFunction<*>): Array<out String> =
-        baseCommand.secondaryNames
-}
-
-internal abstract class AbstractReflectionCommand
-@JvmOverloads constructor(
-    owner: CommandOwner,
-    primaryName: String,
-    secondaryNames: Array<out String>,
-    description: String = "<no description available>",
-    parentPermission: Permission = owner.parentPermission,
-    prefixOptional: Boolean = false,
-) : Command, AbstractCommand(
-    owner,
-    primaryName = primaryName,
-    secondaryNames = secondaryNames,
-    description = description,
-    parentPermission = parentPermission,
-    prefixOptional = prefixOptional
-), CommandArgumentContextAware {
-    internal abstract val subCommandAnnotationResolver: SubCommandAnnotationResolver
-
-    @JvmField
-    @Suppress("PropertyName")
-    internal var _usage: String = "<not yet initialized>"
-
-    override val usage: String  // initialized by subCommand reflection
-        get() {
-            subCommands // ensure init
-            return _usage
-        }
-
-    abstract suspend fun CommandSender.onDefault(rawArgs: MessageChain)
-
-    internal val defaultSubCommand: DefaultSubCommandDescriptor by lazy {
-        DefaultSubCommandDescriptor(
-            "",
-            createOrFindCommandPermission(parentPermission),
-            onCommand = { sender: CommandSender, args: MessageChain ->
-                sender.onDefault(args)
-            }
-        )
-    }
-
-    internal open fun checkSubCommand(subCommands: Array<SubCommandDescriptor>) {
-
-    }
-
-    interface SubCommandAnnotationResolver {
-        fun hasAnnotation(baseCommand: AbstractReflectionCommand, function: KFunction<*>): Boolean
-        fun getSubCommandNames(baseCommand: AbstractReflectionCommand, function: KFunction<*>): Array<out String>
-    }
-
-    internal val subCommands: Array<SubCommandDescriptor> by lazy {
-        this::class.declaredFunctions.filter { subCommandAnnotationResolver.hasAnnotation(this, it) }
-            .also { subCommandFunctions ->
-                // overloading not yet supported
-                val overloadFunction = subCommandFunctions.groupBy { it.name }.entries.firstOrNull { it.value.size > 1 }
-                if (overloadFunction != null) {
-                    error("Sub command overloading is not yet supported. (at ${this::class.qualifiedNameOrTip}.${overloadFunction.key})")
-                }
-            }.map { function ->
-                createSubCommand(function, context)
-            }.toTypedArray().also {
-                _usage = it.createUsage(this)
-            }.also { checkSubCommand(it) }
-    }
-
-    internal val bakedCommandNameToSubDescriptorArray: Map<Array<String>, SubCommandDescriptor> by lazy {
-        kotlin.run {
-            val map = LinkedHashMap<Array<String>, SubCommandDescriptor>(subCommands.size * 2)
-            for (descriptor in subCommands) {
-                for (name in descriptor.bakedSubNames) {
-                    map[name] = descriptor
-                }
-            }
-            map.toSortedMap { o1, o2 -> o1!!.contentHashCode() - o2!!.contentHashCode() }
-        }
-    }
-
-    internal class DefaultSubCommandDescriptor(
-        val description: String,
-        val permission: Permission,
-        val onCommand: suspend (sender: CommandSender, rawArgs: MessageChain) -> Unit,
-    )
-
-    internal inner class SubCommandDescriptor(
-        val names: Array<out String>,
-        val params: Array<CommandParameter<*>>,
-        val description: String,
-        val permission: Permission,
-        val onCommand: suspend (sender: CommandSender, parsedArgs: Array<out Any>) -> Boolean,
-        val context: CommandArgumentContext,
-    ) {
-        val usage: String = createUsage(this@AbstractReflectionCommand)
-
-        internal suspend fun parseAndExecute(
-            sender: CommandSender,
-            argsWithSubCommandNameNotRemoved: MessageChain,
-            removeSubName: Boolean,
-        ) {
-            val args = parseArgs(sender, argsWithSubCommandNameNotRemoved, if (removeSubName) 1 else 0)
-            if (!this.permission.testPermission(sender)) {
-                sender.sendMessage(usage) // TODO: 2020/8/26 #127
-                return
-            }
-            if (args == null || !onCommand(sender, args)) {
-                sender.sendMessage(usage)
-            }
-        }
-
-        @JvmField
-        internal val bakedSubNames: Array<Array<String>> = names.map { it.bakeSubName() }.toTypedArray()
-        private fun parseArgs(sender: CommandSender, rawArgs: MessageChain, offset: Int): Array<out Any>? {
-            if (rawArgs.size < offset + this.params.size)
-                return null
-            //require(rawArgs.size >= offset + this.params.size) { "No enough args. Required ${params.size}, but given ${rawArgs.size - offset}" }
-
-            return Array(this.params.size) { index ->
-                val param = params[index]
-                val rawArg = rawArgs[offset + index]
-                when (rawArg) {
-                    is PlainText -> context[param.type]?.parse(rawArg.content, sender)
-                    is MessageContent -> context[param.type]?.parse(rawArg, sender)
-                    else -> throw IllegalArgumentException("Illegal Message kind: ${rawArg.kClassQualifiedNameOrTip}")
-                } ?: error("Cannot find a parser for $rawArg")
-            }
-        }
-    }
-
-    /**
-     * @param rawArgs 元素类型必须为 [SingleMessage] 或 [String], 且已经经过扁平化处理. 否则抛出异常 [IllegalArgumentException]
-     */
-    internal fun matchSubCommand(rawArgs: MessageChain): SubCommandDescriptor? {
-        val maxCount = rawArgs.size
-        var cur = 0
-        bakedCommandNameToSubDescriptorArray.forEach { (name, descriptor) ->
-            if (name.size != cur) {
-                if (cur++ == maxCount) return null
-            }
-            if (name.contentEqualsOffset(rawArgs, length = cur)) {
-                return descriptor
-            }
-        }
-        return null
-    }
-}
-
-internal fun <T> Array<T>.contentEqualsOffset(other: MessageChain, length: Int): Boolean {
-    repeat(length) { index ->
-        if (!other[index].toString().equals(this[index].toString(), ignoreCase = true)) {
-            return false
-        }
-    }
-    return true
-}
-
-internal val ILLEGAL_SUB_NAME_CHARS = "\\/!@#$%^&*()_+-={}[];':\",.<>?`~".toCharArray()
-internal fun String.isValidSubName(): Boolean = ILLEGAL_SUB_NAME_CHARS.none { it in this }
-internal fun String.bakeSubName(): Array<String> = split(' ').filterNot { it.isBlank() }.toTypedArray()
-
-internal fun Any.flattenCommandComponents(): MessageChain = buildMessageChain {
-    when (this@flattenCommandComponents) {
-        is PlainText -> this@flattenCommandComponents.content.splitToSequence(' ').filterNot { it.isBlank() }
-            .forEach { +PlainText(it) }
-        is CharSequence -> this@flattenCommandComponents.splitToSequence(' ').filterNot { it.isBlank() }
-            .forEach { +PlainText(it) }
-        is SingleMessage -> add(this@flattenCommandComponents)
-        is Array<*> -> this@flattenCommandComponents.forEach { if (it != null) addAll(it.flattenCommandComponents()) }
-        is Iterable<*> -> this@flattenCommandComponents.forEach { if (it != null) addAll(it.flattenCommandComponents()) }
-        else -> add(this@flattenCommandComponents.toString())
-    }
-}
-
-internal inline fun <reified T : Annotation> KAnnotatedElement.hasAnnotation(): Boolean =
-    findAnnotation<T>() != null
-
-internal val KClass<*>.qualifiedNameOrTip: String get() = this.qualifiedName ?: "<anonymous class>"
-
-internal fun Array<AbstractReflectionCommand.SubCommandDescriptor>.createUsage(baseCommand: AbstractReflectionCommand): String =
-    buildString {
-        appendLine(baseCommand.description)
-        appendLine()
-
-        for (subCommandDescriptor in this@createUsage) {
-            appendLine(subCommandDescriptor.usage)
-        }
-    }.trimEnd()
-
-internal fun AbstractReflectionCommand.SubCommandDescriptor.createUsage(baseCommand: AbstractReflectionCommand): String =
-    buildString {
-        if (baseCommand.prefixOptional) {
-            append("(")
-            append(CommandManager.commandPrefix)
-            append(")")
-        } else {
-            append(CommandManager.commandPrefix)
-        }
-        if (baseCommand is CompositeCommand) {
-            append(baseCommand.primaryName)
-            append(" ")
-        }
-        append(names.first())
-        append(" ")
-        append(params.joinToString(" ") { "<${it.name}>" })
-        append("   ")
-        append(description)
-        appendLine()
-    }.trimEnd()
-
-internal fun AbstractReflectionCommand.createSubCommand(
-    function: KFunction<*>,
-    context: CommandArgumentContext,
-): AbstractReflectionCommand.SubCommandDescriptor {
-    val notStatic = !function.hasAnnotation<JvmStatic>()
-    //val overridePermission = null//function.findAnnotation<CompositeCommand.PermissionId>()//optional
-    val subDescription =
-        function.findAnnotation<CompositeCommand.Description>()?.value ?: ""
-
-    fun KClass<*>.isValidReturnType(): Boolean {
-        return when (this) {
-            Boolean::class, Void::class, Unit::class, Nothing::class -> true
-            else -> false
-        }
-    }
-
-    check((function.returnType.classifier as? KClass<*>)?.isValidReturnType() == true) {
-        error("Return type of sub command ${function.name} must be one of the following: kotlin.Boolean, java.lang.Boolean, kotlin.Unit (including implicit), kotlin.Nothing, boolean or void (at ${this::class.qualifiedNameOrTip}.${function.name})")
-    }
-
-    check(!function.returnType.isMarkedNullable) {
-        error("Return type of sub command ${function.name} must not be marked nullable in Kotlin, and must be marked with @NotNull or @NonNull explicitly in Java. (at ${this::class.qualifiedNameOrTip}.${function.name})")
-    }
-
-    val parameters = function.parameters.toMutableList()
-
-    if (notStatic) parameters.removeAt(0) // instance
-
-    var hasSenderParam = false
-    check(parameters.isNotEmpty()) {
-        "Parameters of sub command ${function.name} must not be empty. (Must have CommandSender as its receiver or first parameter or absent, followed by naturally typed params) (at ${this::class.qualifiedNameOrTip}.${function.name})"
-    }
-
-    parameters.forEach { param ->
-        check(!param.isVararg) {
-            "Parameter $param must not be vararg. (at ${this::class.qualifiedNameOrTip}.${function.name}.$param)"
-        }
-    }
-
-    (parameters.first()).let { receiver ->
-        if ((receiver.type.classifier as? KClass<*>)?.isSubclassOf(CommandSender::class) == true) {
-            hasSenderParam = true
-            parameters.removeAt(0)
-        }
-    }
-
-    val commandName =
-        subCommandAnnotationResolver.getSubCommandNames(this, function)
-            .let { namesFromAnnotation ->
-                if (namesFromAnnotation.isNotEmpty()) {
-                    namesFromAnnotation.map(String::toLowerCase).toTypedArray()
-                } else arrayOf(function.name.toLowerCase())
-            }.also { names ->
-                names.forEach {
-                    check(it.isValidSubName()) {
-                        "Name of sub command ${function.name} is invalid"
-                    }
-                }
-            }
-
-    //map parameter
-    val params = parameters.map { param ->
-
-        if (param.isOptional) error("optional parameters are not yet supported. (at ${this::class.qualifiedNameOrTip}.${function.name}.$param)")
-
-        val paramName = param.findAnnotation<CompositeCommand.Name>()?.value ?: param.name ?: "unknown"
-        CommandParameter(
-            paramName,
-            (param.type.classifier as? KClass<*>)
-                ?: throw IllegalArgumentException("unsolved type reference from param " + param.name + ". (at ${this::class.qualifiedNameOrTip}.${function.name}.$param)")
-        )
-    }.toTypedArray()
-
-    return SubCommandDescriptor(
-        commandName,
-        params,
-        subDescription, // overridePermission?.value
-        permission,//overridePermission?.value?.let { PermissionService.INSTANCE[PermissionId.parseFromString(it)] } ?: permission,
-        onCommand = { sender: CommandSender, args: Array<out Any> ->
-            val result = if (notStatic) {
-                if (hasSenderParam) {
-                    function.isSuspend
-                    function.callSuspend(this, sender, *args)
-                } else function.callSuspend(this, *args)
-            } else {
-                if (hasSenderParam) {
-                    function.callSuspend(sender, *args)
-                } else function.callSuspend(*args)
-            }
-
-            checkNotNull(result) { "sub command return value is null (at ${this::class.qualifiedName}.${function.name})" }
-
-            result as? Boolean ?: true // Unit, void is considered as true.
-        },
-        context = context
-    )
-}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/executeCommandInternal.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/command/executeCommandInternal.kt
@ -1,62 +0,0 @@
-/*
- * Copyright 2019-2020 Mamoe Technologies and contributors.
- *
- * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- * Use of this source code is governed by the GNU AFFERO GENERAL PUBLIC LICENSE version 3 license that can be found via the following link.
- *
- * https://github.com/mamoe/mirai/blob/master/LICENSE
- */
-
-package net.mamoe.mirai.console.internal.command
-
-import net.mamoe.mirai.console.command.*
-import net.mamoe.mirai.console.permission.PermissionService.Companion.testPermission
-import net.mamoe.mirai.message.data.MessageChain
-import net.mamoe.mirai.message.data.asMessageChain
-
-@JvmSynthetic
-@Throws(CommandExecutionException::class)
-internal suspend fun CommandSender.executeCommandInternal(
-    command: Command,
-    args: MessageChain,
-    commandName: String,
-    checkPermission: Boolean,
-): CommandExecuteResult {
-    if (checkPermission && !command.permission.testPermission(this)) {
-        return CommandExecuteResult.PermissionDenied(command, commandName)
-    }
-
-    kotlin.runCatching {
-        command.onCommand(this, args)
-    }.fold(
-        onSuccess = {
-            return CommandExecuteResult.Success(
-                commandName = commandName,
-                command = command,
-                args = args
-            )
-        },
-        onFailure = {
-            return CommandExecuteResult.ExecutionFailed(
-                commandName = commandName,
-                command = command,
-                exception = it,
-                args = args
-            )
-        }
-    )
-}
-
-
-@JvmSynthetic
-internal suspend fun CommandSender.executeCommandInternal(
-    messages: Any,
-    commandName: String,
-    checkPermission: Boolean,
-): CommandExecuteResult {
-    val command =
-        CommandManagerImpl.matchCommand(commandName) ?: return CommandExecuteResult.CommandNotFound(commandName)
-    val args = messages.flattenCommandComponents()
-
-    return executeCommandInternal(command, args.drop(1).asMessageChain(), commandName, checkPermission)
-}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/MultiFilePluginDataStorageImpl.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/MultiFilePluginDataStorageImpl.kt
@ -12,7 +12,6 @@ package net.mamoe.mirai.console.internal.data
 import kotlinx.serialization.json.Json
 import net.mamoe.mirai.console.MiraiConsole
 import net.mamoe.mirai.console.data.*
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
 import net.mamoe.mirai.console.util.ConsoleExperimentalApi
 import net.mamoe.mirai.utils.MiraiLogger
 import net.mamoe.mirai.utils.SilentLogger
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/reflectionUtils.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/reflectionUtils.kt
@ -11,14 +11,15 @@ package net.mamoe.mirai.console.internal.data

 import net.mamoe.mirai.console.data.PluginData
 import net.mamoe.mirai.console.data.ValueName
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
-import kotlin.reflect.KClass
-import kotlin.reflect.KParameter
-import kotlin.reflect.KProperty
-import kotlin.reflect.KType
+import kotlin.reflect.*
 import kotlin.reflect.full.findAnnotation
 import kotlin.reflect.full.isSubclassOf

+internal val KClass<*>.qualifiedNameOrTip: String get() = this.qualifiedName ?: "<anonymous class>"
+
+internal inline fun <reified T : Annotation> KAnnotatedElement.hasAnnotation(): Boolean =
+    findAnnotation<T>() != null
+
@Suppress("UNCHECKED_CAST")
 internal inline fun <reified T : Any> KType.toKClass(): KClass<out T> {
    val clazz = requireNotNull(classifier as? KClass<T>) { "Unsupported classifier: $classifier" }
@ -54,6 +55,12 @@ internal fun KType.classifierAsKClass() = when (val t = classifier) {
    else -> error("Only KClass supported as classifier, got $t")
 } as KClass<Any>

+@Suppress("UNCHECKED_CAST")
+internal fun KType.classifierAsKClassOrNull() = when (val t = classifier) {
+    is KClass<*> -> t
+    else -> null
+} as KClass<Any>?
+
@JvmSynthetic
 internal fun <T : Any> KClass<T>.createInstanceOrNull(): T? {
    val noArgsConstructor = constructors.singleOrNull { it.parameters.all(KParameter::isOptional) }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/valueFromKTypeImpl.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/data/valueFromKTypeImpl.kt
@ -16,7 +16,6 @@ import net.mamoe.mirai.console.data.PluginData
 import net.mamoe.mirai.console.data.SerializableValue.Companion.serializableValueWith
 import net.mamoe.mirai.console.data.SerializerAwareValue
 import net.mamoe.mirai.console.data.valueFromKType
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
 import kotlin.contracts.contract
 import kotlin.reflect.KClass
 import kotlin.reflect.KType
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/extension/BuiltInSingletonExtensionSelector.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/extension/BuiltInSingletonExtensionSelector.kt
@ -52,7 +52,7 @@ internal object BuiltInSingletonExtensionSelector : SingletonExtensionSelector {
        val candidatesList = candidates.toList()

        for ((index, candidate) in candidatesList.withIndex()) {
-            MiraiConsole.mainLogger.info { "${index + 1}. '${candidate.extension}' from '${candidate.plugin.name}'" }
+            MiraiConsole.mainLogger.info { "${index + 1}. '${candidate.extension}' from '${candidate.plugin?.name ?: "<builtin>"}'" }
        }

        MiraiConsole.mainLogger.info { "Please choose a number from 1 to ${candidatesList.count()}" }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/extension/ComponentStorageInternal.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/extension/ComponentStorageInternal.kt
@ -20,12 +20,15 @@ import java.util.concurrent.CopyOnWriteArraySet
 import kotlin.contracts.contract
 import kotlin.reflect.KClass

+/**
+ * The [ComponentStorage] containing all components provided by Mirai Console internals and installed plugins.
+ */
 internal object GlobalComponentStorage : AbstractConcurrentComponentStorage()
 internal interface ExtensionRegistry<out E : Extension> {
-    val plugin: Plugin
+    val plugin: Plugin?
    val extension: E

-    operator fun component1(): Plugin {
+    operator fun component1(): Plugin? {
        return this.plugin
    }

@ -35,21 +38,27 @@ internal interface ExtensionRegistry<out E : Extension> {
 }

 internal class LazyExtensionRegistry<out E : Extension>(
-    override val plugin: Plugin,
+    override val plugin: Plugin?,
    initializer: () -> E,
 ) : ExtensionRegistry<E> {
    override val extension: E by lazy { initializer() }
 }

 internal data class DataExtensionRegistry<out E : Extension>(
-    override val plugin: Plugin,
+    override val plugin: Plugin?,
    override val extension: E,
 ) : ExtensionRegistry<E>

 internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {
    @Suppress("UNCHECKED_CAST")
    internal fun <T : Extension> ExtensionPoint<out T>.getExtensions(): Set<ExtensionRegistry<T>> {
-        return instances.getOrPut(this, ::CopyOnWriteArraySet) as Set<ExtensionRegistry<T>>
+        val userDefined = instances.getOrPut(this, ::CopyOnWriteArraySet) as Set<ExtensionRegistry<T>>
+
+        val builtins = if (this is InstanceExtensionPoint<*, *>) {
+            this.builtinImplementations.mapTo(HashSet()) { DataExtensionRegistry(null, it) } as Set<ExtensionRegistry<T>>
+        } else null
+
+        return builtins?.plus(userDefined) ?: userDefined
    }

    internal fun mergeWith(another: AbstractConcurrentComponentStorage) {
@ -68,7 +77,7 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {

    @Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
    @kotlin.internal.LowPriorityInOverloadResolution
-    internal inline fun <T : Extension> ExtensionPoint<out T>.withExtensions(block: T.(plugin: Plugin) -> Unit) {
+    internal inline fun <T : Extension> ExtensionPoint<out T>.withExtensions(block: T.(plugin: Plugin?) -> Unit) {
        contract {
            callsInPlace(block)
        }
@ -128,11 +137,11 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {

    internal fun <T : Extension> ExtensionPoint<out T>.throwExtensionException(
        extension: T,
-        plugin: Plugin,
+        plugin: Plugin?,
        throwable: Throwable,
    ) {
        throw ExtensionException(
-            "Exception while executing extension '${extension.kClassQualifiedNameOrTip}' provided by plugin '${plugin.name}', registered for '${this.extensionType.qualifiedName}'",
+            "Exception while executing extension '${extension.kClassQualifiedNameOrTip}' provided by plugin '${plugin?.name ?: "<builtin>"}', registered for '${this.extensionType.qualifiedName}'",
            throwable
        )
    }
@ -142,7 +151,7 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {

    @Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
    @kotlin.internal.LowPriorityInOverloadResolution
-    internal inline fun <T : Extension> ExtensionPoint<T>.useExtensions(block: (extension: T, plugin: Plugin) -> Unit): Unit =
+    internal inline fun <T : Extension> ExtensionPoint<T>.useExtensions(block: (extension: T, plugin: Plugin?) -> Unit): Unit =
        withExtensions(block)

    val instances: MutableMap<ExtensionPoint<*>, MutableSet<ExtensionRegistry<*>>> = ConcurrentHashMap()
@ -154,6 +163,15 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {
        instances.getOrPut(extensionPoint, ::CopyOnWriteArraySet).add(DataExtensionRegistry(plugin, extensionInstance))
    }

+    @JvmName("contribute1")
+    fun <T : Extension> contribute(
+        extensionPoint: ExtensionPoint<T>,
+        plugin: Plugin?,
+        extensionInstance: T,
+    ) {
+        instances.getOrPut(extensionPoint, ::CopyOnWriteArraySet).add(DataExtensionRegistry(plugin, extensionInstance))
+    }
+
    override fun <T : Extension> contribute(
        extensionPoint: ExtensionPoint<T>,
        plugin: Plugin,
@ -161,4 +179,13 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {
    ) {
        instances.getOrPut(extensionPoint, ::CopyOnWriteArraySet).add(LazyExtensionRegistry(plugin, lazyInstance))
    }
+
+    @JvmName("contribute1")
+    fun <T : Extension> contribute(
+        extensionPoint: ExtensionPoint<T>,
+        plugin: Plugin?,
+        lazyInstance: () -> T,
+    ) {
+        instances.getOrPut(extensionPoint, ::CopyOnWriteArraySet).add(LazyExtensionRegistry(plugin, lazyInstance))
+    }
 }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/plugin/JvmPluginInternal.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/plugin/JvmPluginInternal.kt
@ -48,7 +48,7 @@ internal abstract class JvmPluginInternal(

    final override val parentPermission: Permission by lazy {
        PermissionService.INSTANCE.register(
-            PermissionService.INSTANCE.allocatePermissionIdForPlugin(this, "*", PermissionService.PluginPermissionIdRequestType.ROOT_PERMISSION),
+            PermissionService.INSTANCE.allocatePermissionIdForPlugin(this, "*", PermissionService.PluginPermissionIdRequestType.PLUGIN_ROOT_PERMISSION),
            "The base permission"
        )
    }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/plugin/PluginManagerImpl.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/internal/plugin/PluginManagerImpl.kt
@ -148,7 +148,7 @@ internal object PluginManagerImpl : PluginManager, CoroutineScope by MiraiConsol
        var count = 0
        GlobalComponentStorage.run {
            PluginLoaderProvider.useExtensions { ext, plugin ->
-                logger.info { "Loaded PluginLoader ${ext.instance} from ${plugin.name}" }
+                logger.info { "Loaded PluginLoader ${ext.instance} from ${plugin?.name ?: "<builtin>"}" }
                _pluginLoaders.add(ext.instance)
                count++
            }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/Permission.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/Permission.kt
@ -7,6 +7,8 @@
 * https://github.com/mamoe/mirai/blob/master/LICENSE
 */

+@file:Suppress("unused")
+
 package net.mamoe.mirai.console.permission

 import net.mamoe.mirai.console.command.BuiltInCommands
@ -65,10 +67,10 @@ public interface Permission {
         * @see RootPermission 推荐 Kotlin 用户使用.
         */
        @JvmStatic
-        public fun getRootPermission(): Permission = PermissionService.INSTANCE.rootPermission
+        public fun getRootPermission(): Permission = RootPermission

        /**
-         * 递归获取 [Permission.parent], `permission.parent.parent`, permission.parent.parent` ... 直到 [Permission.parent] 为它自己.
+         * 递归获取 [Permission.parent], `permission.parent.parent`, permission.parent.parent.parent` ... 直到 [Permission.parent] 为它自己.
         */
        @get:JvmStatic
        public val Permission.parentsWithSelf: Sequence<Permission>
@ -82,5 +84,5 @@ public interface Permission {
 * 根权限. 是所有权限的父权限. 权限 ID 为 "*:*"
 */
@get:JvmSynthetic
-public val RootPermission: Permission
+public inline val RootPermission: Permission // It might be removed in the future, so make it inline to avoid ABI changes.
    get() = PermissionService.INSTANCE.rootPermission
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/PermissionId.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/PermissionId.kt
@ -35,20 +35,20 @@ public data class PermissionId(
            "' ' is not allowed in namespace"
        }
        require(name.none { it.isWhitespace() }) {
-            "' ' is not allowed in id"
+            "' ' is not allowed in name"
        }

        require(!namespace.contains(':')) {
            "':' is not allowed in namespace"
        }
        require(!name.contains(':')) {
-            "':' is not allowed in id"
+            "':' is not allowed in name"
        }
    }

    public object PermissionIdAsStringSerializer : KSerializer<PermissionId> by String.serializer().map(
        serializer = { it.namespace + ":" + it.name },
-        deserializer = { it.split(':').let { (namespace, id) -> PermissionId(namespace, id) } }
+        deserializer = ::parseFromString
    )

    /**
@ -76,11 +76,11 @@ public data class PermissionId(
         */
        @JvmStatic
        @Throws(IllegalArgumentException::class)
-        public fun checkPermissionIdName(@ResolveContext(PERMISSION_NAME) value: String) {
+        public fun checkPermissionIdName(@ResolveContext(PERMISSION_NAME) name: String) {
            when {
-                value.isBlank() -> throw IllegalArgumentException("PermissionId.name should not be blank.")
-                value.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces is not yet allowed in PermissionId.name.")
-                value.contains(':') -> throw IllegalArgumentException("':' is forbidden in PermissionId.name.")
+                name.isBlank() -> throw IllegalArgumentException("PermissionId.name should not be blank.")
+                name.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces are not yet allowed in PermissionId.name.")
+                name.contains(':') -> throw IllegalArgumentException("':' is forbidden in PermissionId.name.")
            }
        }

@ -89,11 +89,11 @@ public data class PermissionId(
         */
        @JvmStatic
        @Throws(IllegalArgumentException::class)
-        public fun checkPermissionIdNamespace(@ResolveContext(PERMISSION_NAME) value: String) {
+        public fun checkPermissionIdNamespace(@ResolveContext(PERMISSION_NAME) namespace: String) {
            when {
-                value.isBlank() -> throw IllegalArgumentException("PermissionId.namespace should not be blank.")
-                value.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces is not yet allowed in PermissionId.namespace.")
-                value.contains(':') -> throw IllegalArgumentException("':' is forbidden in PermissionId.namespace.")
+                namespace.isBlank() -> throw IllegalArgumentException("PermissionId.namespace should not be blank.")
+                namespace.any { it.isWhitespace() } -> throw IllegalArgumentException("Spaces are not yet allowed in PermissionId.namespace.")
+                namespace.contains(':') -> throw IllegalArgumentException("':' is forbidden in PermissionId.namespace.")
            }
        }
    }
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/PermissionService.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/permission/PermissionService.kt
@ -129,10 +129,10 @@ public interface PermissionService<P : Permission> {
    /** [Plugin] 尝试分配的 [PermissionId] 来源 */
    public enum class PluginPermissionIdRequestType {
        /** For [Plugin.parentPermission] */
-        ROOT_PERMISSION,
+        PLUGIN_ROOT_PERMISSION,

        /** For [Plugin.permissionId] */
-        PERMISSION_ID
+        NORMAL
    }

    public companion object {
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/plugin/jvm/AbstractJvmPlugin.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/plugin/jvm/AbstractJvmPlugin.kt
@ -39,7 +39,7 @@ public abstract class AbstractJvmPlugin @JvmOverloads constructor(
    public final override val loader: JvmPluginLoader get() = super<JvmPluginInternal>.loader

    public final override fun permissionId(name: String): PermissionId =
-        PermissionService.INSTANCE.allocatePermissionIdForPlugin(this, name, PermissionService.PluginPermissionIdRequestType.PERMISSION_ID)
+        PermissionService.INSTANCE.allocatePermissionIdForPlugin(this, name, PermissionService.PluginPermissionIdRequestType.NORMAL)

    /**
     * 重载 [PluginData]
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/ContactUtils.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/ContactUtils.kt
@ -12,7 +12,7 @@
 package net.mamoe.mirai.console.util

 import net.mamoe.mirai.Bot
-import net.mamoe.mirai.console.internal.command.qualifiedNameOrTip
+import net.mamoe.mirai.console.internal.data.qualifiedNameOrTip
 import net.mamoe.mirai.contact.*

 /**
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/MessageUtils.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/MessageUtils.kt
@ -0,0 +1,25 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.util
+
+import net.mamoe.mirai.message.data.MessageChain
+import net.mamoe.mirai.message.data.MessageContent
+
+@ConsoleExperimentalApi
+public object MessageUtils {
+    @JvmStatic
+    public fun MessageChain.messageContentsSequence(): Sequence<MessageContent> = asSequence().filterIsInstance<MessageContent>()
+
+    @JvmStatic
+    public fun MessageChain.firstContent(): MessageContent = messageContentsSequence().first()
+
+    @JvmStatic
+    public fun MessageChain.firstContentOrNull(): MessageContent? = messageContentsSequence().firstOrNull()
+}
--- a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/StandardUtils.kt
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/StandardUtils.kt
@ -0,0 +1,34 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.console.util
+
+import kotlin.contracts.contract
+
+/**
+ * Perform `this as? T`.
+ */
+@JvmSynthetic
+public inline fun <reified T : Any> Any?.safeCast(): T? {
+    contract {
+        returnsNotNull() implies (this@safeCast is T)
+    }
+    return this as? T
+}
+
+/**
+ * Perform `this as T`.
+ */
+@JvmSynthetic
+public inline fun <reified T : Any> Any?.cast(): T {
+    contract {
+        returns() implies (this@cast is T)
+    }
+    return this as T
+}
--- a/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/TestMiraiConosle.kt
+++ b/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/TestMiraiConosle.kt
@ -89,7 +89,7 @@ internal object Testing {
    internal var cont: Continuation<Any?>? = null

    @Suppress("UNCHECKED_CAST")
-    suspend fun <R> withTesting(timeout: Long = 5000L, block: suspend () -> Unit): R {
+    suspend fun <R> withTesting(timeout: Long = 50000L, block: suspend () -> Unit): R {
        @Suppress("RemoveExplicitTypeArguments") // bug
        return if (timeout != -1L) {
            withTimeout<R>(timeout) {
--- a/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/command/TestCommand.kt
+++ b/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/command/TestCommand.kt
@ -16,14 +16,14 @@ import kotlinx.coroutines.runBlocking
 import net.mamoe.mirai.console.MiraiConsole
 import net.mamoe.mirai.console.Testing
 import net.mamoe.mirai.console.Testing.withTesting
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.execute
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.getRegisteredCommands
 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.register
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.registeredCommands
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.unregister
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.registerCommand
 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.unregisterAllCommands
-import net.mamoe.mirai.console.command.description.CommandArgumentParser
-import net.mamoe.mirai.console.command.description.buildCommandArgumentContext
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.unregisterCommand
+import net.mamoe.mirai.console.command.descriptor.CommandValueArgumentParser
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
+import net.mamoe.mirai.console.command.descriptor.buildCommandArgumentContext
 import net.mamoe.mirai.console.initTestEnvironment
 import net.mamoe.mirai.console.internal.command.CommandManagerImpl
 import net.mamoe.mirai.console.internal.command.flattenCommandComponents
@ -38,7 +38,12 @@ object TestCompositeCommand : CompositeCommand(
    "testComposite", "tsC"
 ) {
    @SubCommand
-    fun mute(seconds: Int) {
+    fun mute(seconds: Int = 60) {
+        Testing.ok(seconds)
+    }
+
+    @SubCommand
+    fun mute(target: Long, seconds: Int) {
        Testing.ok(seconds)
    }
 }
@ -54,6 +59,7 @@ internal val sender by lazy { ConsoleCommandSender }
 internal val owner by lazy { ConsoleCommandOwner }


+@OptIn(ExperimentalCommandDescriptors::class)
 internal class TestCommand {
    companion object {
        @JvmStatic
@ -72,26 +78,31 @@ internal class TestCommand {
    @Test
    fun testRegister() {
        try {
-            ConsoleCommandOwner.unregisterAllCommands() // builtins
+            unregisterAllCommands(ConsoleCommandOwner) // builtins
+            unregisterCommand(TestSimpleCommand)

            assertTrue(TestCompositeCommand.register())
            assertFalse(TestCompositeCommand.register())

-            assertEquals(1, ConsoleCommandOwner.registeredCommands.size)
+            assertEquals(1, getRegisteredCommands(ConsoleCommandOwner).size)

            assertEquals(1, CommandManagerImpl._registeredCommands.size)
-            assertEquals(2, CommandManagerImpl.requiredPrefixCommandMap.size)
+            assertEquals(2,
+                CommandManagerImpl.requiredPrefixCommandMap.size,
+                CommandManagerImpl.requiredPrefixCommandMap.entries.joinToString { it.toString() })
        } finally {
-            TestCompositeCommand.unregister()
+            unregisterCommand(TestCompositeCommand)
        }
    }

    @Test
    fun testSimpleExecute() = runBlocking {
+        TestSimpleCommand.withRegistration {
            assertEquals("test", withTesting<MessageChain> {
                assertSuccess(TestSimpleCommand.execute(sender, "test"))
            }.contentToString())
        }
+    }

    @Test
    fun `test flattenCommandArgs`() {
@ -105,15 +116,18 @@ internal class TestCommand {

    @Test
    fun testSimpleArgsSplitting() = runBlocking {
+        TestSimpleCommand.withRegistration {
            assertEquals(arrayOf("test", "ttt", "tt").joinToString(), withTesting<MessageChain> {
                assertSuccess(TestSimpleCommand.execute(sender, PlainText("test ttt tt")))
            }.joinToString())
        }
+    }

    val image = Image("/f8f1ab55-bf8e-4236-b55e-955848d7069f")

    @Test
    fun `PlainText and Image args splitting`() = runBlocking {
+        TestSimpleCommand.withRegistration {
            val result = withTesting<MessageChain> {
                assertSuccess(TestSimpleCommand.execute(sender, buildMessageChain {
                    +"test"
@ -124,6 +138,7 @@ internal class TestCommand {
            assertEquals<Any>(arrayOf("test", image, "tt").joinToString(), result.toTypedArray().joinToString())
            assertSame(image, result[1])
        }
+    }

    @Test
    fun `test throw Exception`() {
@ -134,20 +149,30 @@ internal class TestCommand {

    @Test
    fun `executing command by string command`() = runBlocking {
-        TestCompositeCommand.register()
+        TestCompositeCommand.withRegistration {
            val result = withTesting<Int> {
                assertSuccess(sender.executeCommand("/testComposite mute 1"))
            }

            assertEquals(1, result)
        }
+    }
+
+    @Test
+    fun `composite command descriptors`() {
+        val overloads = TestCompositeCommand.overloads
+        assertEquals("CommandSignatureVariant(<mute>, seconds: Int = ...)", overloads[0].toString())
+        assertEquals("CommandSignatureVariant(<mute>, target: Long, seconds: Int)", overloads[1].toString())
+    }

    @Test
    fun `composite command executing`() = runBlocking {
+        TestCompositeCommand.withRegistration {
            assertEquals(1, withTesting {
                assertSuccess(TestCompositeCommand.execute(sender, "mute 1"))
            })
        }
+    }

    @Test
    fun `composite sub command resolution conflict`() {
@ -164,19 +189,19 @@ internal class TestCommand {

                @Suppress("UNUSED_PARAMETER")
                @SubCommand
-                fun mute(seconds: Int, arg2: Int) {
+                fun mute(seconds: Int, arg2: Int = 1) {
                    Testing.ok(2)
                }
            }

-            assertFailsWith<IllegalStateException> {
-                composite.register()
-            }
-            /*
+            registerCommand(composite)
+
+            println(composite.overloads.joinToString())
+
            composite.withRegistration {
-                assertEquals(1, withTesting { execute(sender, "tr", "mute 123") }) // one args, resolves to mute(Int)
-                assertEquals(2, withTesting { execute(sender, "tr", "mute 123 123") })
-            }*/
+                assertEquals(1, withTesting { assertSuccess(composite.execute(sender, "mute 123")) }) // one arg, resolves to mute(Int)
+                assertEquals(2, withTesting { assertSuccess(composite.execute(sender, "mute 123 1")) }) // two arg, resolved to mute(Int, Int)
+            }
        }
    }

@ -184,19 +209,20 @@ internal class TestCommand {
    fun `composite sub command parsing`() {
        runBlocking {
            class MyClass(
-                val value: Int
+                val value: Int,
            )

            val composite = object : CompositeCommand(
                ConsoleCommandOwner,
                "test22",
                overrideContext = buildCommandArgumentContext {
-                    add(object : CommandArgumentParser<MyClass> {
+                    add(object : CommandValueArgumentParser<MyClass> {
                        override fun parse(raw: String, sender: CommandSender): MyClass {
                            return MyClass(raw.toInt())
                        }

                        override fun parse(raw: MessageContent, sender: CommandSender): MyClass {
+                            if (raw is PlainText) return parse(raw.content, sender)
                            assertSame(image, raw)
                            return MyClass(2)
                        }
@ -210,12 +236,14 @@ internal class TestCommand {
            }

            composite.withRegistration {
-                assertEquals(333, withTesting<MyClass> { execute(sender, "mute 333") }.value)
+                assertEquals(333, withTesting<MyClass> { assertSuccess(execute(sender, "mute 333")) }.value)
                assertEquals(2, withTesting<MyClass> {
+                    assertSuccess(
                        execute(sender, buildMessageChain {
                            +"mute"
                            +image
                        })
+                    )
                }.value)
            }
        }
@ -238,8 +266,76 @@ internal class TestCommand {
            }
        }
    }
+
+    @Test
+    fun `test optional argument command`() {
+        runBlocking {
+            val optionCommand = object : CompositeCommand(
+                ConsoleCommandOwner,
+                "testOptional"
+            ) {
+                @SubCommand
+                fun optional(arg1: String, arg2: String = "Here is optional", arg3: String? = null) {
+                    println(arg1)
+                    println(arg2)
+                    println(arg3)
+//                    println(arg3)
+                    Testing.ok(Unit)
+                }
+            }
+            optionCommand.withRegistration {
+                withTesting<Unit> {
+                    assertSuccess(sender.executeCommand("/testOptional optional 1"))
+                }
+            }
+        }
    }

-internal fun assertSuccess(result: CommandExecuteResult) {
-    assertTrue(result.isSuccess(), result.toString())
+    @Test
+    fun `test vararg`() {
+        runBlocking {
+            val optionCommand = object : CompositeCommand(
+                ConsoleCommandOwner,
+                "test"
+            ) {
+                @SubCommand
+                fun vararg(arg1: Int, vararg x: String) {
+                    assertEquals(1, arg1)
+                    Testing.ok(x)
+                }
+            }
+            optionCommand.withRegistration {
+                assertArrayEquals(
+                    emptyArray<String>(),
+                    withTesting {
+                        assertSuccess(sender.executeCommand("/test vararg 1"))
+                    }
+                )
+
+                assertArrayEquals(
+                    arrayOf("s"),
+                    withTesting<Array<String>> {
+                        assertSuccess(sender.executeCommand("/test vararg 1 s"))
+                    }
+                )
+                assertArrayEquals(
+                    arrayOf("s", "s", "s"),
+                    withTesting {
+                        assertSuccess(sender.executeCommand("/test vararg 1 s s s"))
+                    }
+                )
+            }
+        }
+    }
+}
+
+fun <T> assertArrayEquals(expected: Array<out T>, actual: Array<out T>, message: String? = null) {
+    asserter.assertEquals(message, expected.contentToString(), actual.contentToString())
+}
+
+@OptIn(ExperimentalCommandDescriptors::class)
+internal fun assertSuccess(result: CommandExecuteResult) {
+    if (result.isFailure()) {
+        throw result.exception ?: AssertionError(result.toString())
+    }
 }
--- a/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/command/commanTestingUtil.kt
+++ b/backend/mirai-console/src/test/kotlin/net/mamoe/mirai/console/command/commanTestingUtil.kt
@ -10,13 +10,13 @@
 package net.mamoe.mirai.console.command

 import net.mamoe.mirai.console.command.CommandManager.INSTANCE.register
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.unregister
+import net.mamoe.mirai.console.command.CommandManager.INSTANCE.unregisterCommand

 inline fun <T : Command, R> T.withRegistration(block: T.() -> R): R {
    this.register()
    try {
        return block()
    } finally {
-        this.unregister()
+        unregisterCommand(this)
    }
 }
--- a/docs/Commands.md
+++ b/docs/Commands.md
@ -37,9 +37,9 @@
 [`RawCommand`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/RawCommand.kt
 [`CommandManager`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandManager.kt
 [`CommandSender`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/CommandSender.kt
-[`CommandArgumentParser`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentParser.kt
-[`CommandArgumentContext`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentContext.kt
-[`CommandArgumentContext.BuiltIns`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentContext.kt#L66
+[`CommandArgumentParser`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandArgumentParser.kt
+[`CommandArgumentContext`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandArgumentContext.kt
+[`CommandArgumentContext.BuiltIns`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandArgumentContext.kt#L66

 [`MessageScope`]: ../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/util/MessageScope.kt

@ -113,7 +113,7 @@ interface CommandArgumentParser<out T : Any> {
 支持原生数据类型，`Contact` 及其子类，`Bot`。

 #### 构建 [`CommandArgumentContext`]
-查看源码内注释：[CommandArgumentContext.kt: Line 146](../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/description/CommandArgumentContext.kt#L146-L183)
+查看源码内注释：[CommandArgumentContext.kt: Line 146](../backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/command/descriptor/CommandArgumentContext.kt#L146-L183)

 ### 支持参数解析的 [`Command`] 实现
 Mirai Console 内建 [`SimpleCommand`] 与 [`CompositeCommand`] 拥有 [`CommandArgumentContext`]，在处理参数时会首先解析参数再传递给插件的实现。
--- a/frontend/mirai-console-terminal/src/main/kotlin/net/mamoe/mirai/console/terminal/ConsoleThread.kt
+++ b/frontend/mirai-console-terminal/src/main/kotlin/net/mamoe/mirai/console/terminal/ConsoleThread.kt
@ -15,11 +15,8 @@ import kotlinx.coroutines.CoroutineName
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import net.mamoe.mirai.console.MiraiConsole
-import net.mamoe.mirai.console.command.BuiltInCommands
-import net.mamoe.mirai.console.command.CommandExecuteStatus
-import net.mamoe.mirai.console.command.CommandManager
-import net.mamoe.mirai.console.command.CommandManager.INSTANCE.executeCommand
-import net.mamoe.mirai.console.command.ConsoleCommandSender
+import net.mamoe.mirai.console.command.*
+import net.mamoe.mirai.console.command.descriptor.ExperimentalCommandDescriptors
 import net.mamoe.mirai.console.terminal.noconsole.NoConsole
 import net.mamoe.mirai.console.util.ConsoleInternalApi
 import net.mamoe.mirai.console.util.requestInput
@ -29,7 +26,7 @@ import org.jline.reader.UserInterruptException

 val consoleLogger by lazy { DefaultLogger("console") }

-@OptIn(ConsoleInternalApi::class, ConsoleTerminalExperimentalApi::class)
+@OptIn(ConsoleInternalApi::class, ConsoleTerminalExperimentalApi::class, ExperimentalCommandDescriptors::class)
 internal fun startupConsoleThread() {
    if (terminal is NoConsole) return

@ -65,6 +62,9 @@ internal fun startupConsoleThread() {
                when (result.status) {
                    CommandExecuteStatus.SUCCESSFUL -> {
                    }
+                    CommandExecuteStatus.ILLEGAL_ARGUMENT -> {
+                        result.exception?.message?.let { consoleLogger.warning(it) }
+                    }
                    CommandExecuteStatus.EXECUTION_EXCEPTION -> {
                        result.exception?.let(consoleLogger::error)
                    }
--- a/gradle.properties
+++ b/gradle.properties
@ -1,2 +1,3 @@
 # style guide
 kotlin.code.style=official
+org.gradle.vfs.watch=true
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@ -1,5 +1,5 @@
 #Wed Mar 04 22:27:09 CST 2020
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStorePath=wrapper/dists